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FKIE_CVE-2026-84378

Vulnerability from fkie_nvd - Published: 2026-09-02 18:21 - Updated: 2026-09-02 19:18
Severity
5.9 (Medium) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Summary
HTTPX2 is a next generation HTTP client for Python. From 2.5.0 until 2.10.0, the HTTPX2 Server-Sent Events parser in src/httpx2/httpx2/_sse.py repeatedly copies and rescans buffered text in _SSELineDecoder.decode() when an attacker-controlled or compromised SSE endpoint splits one unterminated line across many response chunks. The behavior affects httpx2.Client.sse() and httpx2.AsyncClient.sse(), and the total processing work grows quadratically with the line length, allowing a crafted stream to consume excessive CPU and block a synchronous worker or asynchronous event loop. This issue is fixed in version 2.10.0.
References
security-advisories@github.comhttps://github.com/pydantic/httpx2/commit/cbfc0e04ef6507da29ccbb3b9c2e5b23dd693414
security-advisories@github.comhttps://github.com/pydantic/httpx2/pull/1071
security-advisories@github.comhttps://github.com/pydantic/httpx2/pull/1117
security-advisories@github.comhttps://github.com/pydantic/httpx2/releases/tag/v2.10.0
security-advisories@github.comhttps://github.com/pydantic/httpx2/security/advisories/GHSA-f2fp-rgf2-35cp
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "httpx2",
          "vendor": "pydantic",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2.5.0, \u003c 2.10.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "HTTPX2 is a next generation HTTP client for Python. From 2.5.0 until 2.10.0, the HTTPX2 Server-Sent Events parser in src/httpx2/httpx2/_sse.py repeatedly copies and rescans buffered text in _SSELineDecoder.decode() when an attacker-controlled or compromised SSE endpoint splits one unterminated line across many response chunks. The behavior affects httpx2.Client.sse() and httpx2.AsyncClient.sse(), and the total processing work grows quadratically with the line length, allowing a crafted stream to consume excessive CPU and block a synchronous worker or asynchronous event loop. This issue is fixed in version 2.10.0."
    }
  ],
  "id": "CVE-2026-84378",
  "lastModified": "2026-09-02T19:18:07.907",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 5.9,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-84378",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-09-02T19:00:16.905501Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-09-02T18:21:29.153",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/pydantic/httpx2/commit/cbfc0e04ef6507da29ccbb3b9c2e5b23dd693414"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/pydantic/httpx2/pull/1071"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/pydantic/httpx2/pull/1117"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/pydantic/httpx2/releases/tag/v2.10.0"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/pydantic/httpx2/security/advisories/GHSA-f2fp-rgf2-35cp"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-407"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}



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