Vulnerability-Lookup

CVE-2026-26962 (GCVE-0-2026-26962)

Vulnerability from cvelistv5 – Published: 2026-04-02 17:10 – Updated: 2026-04-03 18:13

Title

Rack: Header injection in multipart requests

Summary

Rack is a modular Ruby web server interface. From version 3.2.0 to before version 3.2.6, Rack::Multipart::Parser unfolds folded multipart part headers incorrectly. When a multipart header contains an obs-fold sequence, Rack preserves the embedded CRLF in parsed parameter values such as filename or name instead of removing the folded line break during unfolding. As a result, applications that later reuse those parsed values in HTTP response headers may be vulnerable to downstream header injection or response splitting. This issue has been patched in version 3.2.6.

Severity ?

4.8 (Medium)


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

CWE

CWE-93 - Improper Neutralization of CRLF Sequences ('CRLF Injection')

Assigner

GitHub_M

References

URL

	Vendor	Product	Version
	rack	rack	Affected: >= 3.2.0, < 3.2.6

GHSA-RX22-G9MX-QRHV

Vulnerability from github – Published: 2026-04-02 20:31 – Updated: 2026-04-02 20:31

Summary

Rack's improper unfolding of folded multipart headers preserves CRLF in parsed parameter values

Details

Summary

Rack::Multipart::Parser unfolds folded multipart part headers incorrectly. When a multipart header contains an obs-fold sequence, Rack preserves the embedded CRLF in parsed parameter values such as filename or name instead of removing the folded line break during unfolding.

As a result, applications that later reuse those parsed values in HTTP response headers may be vulnerable to downstream header injection or response splitting.

Details

Rack::Multipart::Parser accepts folded multipart header values and unfolds them during parsing. However, the unfolding behavior does not fully remove the embedded line break sequence from the parsed value.

This means a multipart part header such as:

Content-Disposition: form-data; name="file"; filename="test\r\n foo.txt"

can result in a parsed parameter value that still contains CRLF characters.

The issue is not that Rack creates a second multipart header field. Rather, the problem is that CRLF remains embedded in the parsed metadata value after unfolding. If an application later uses that value in a security-sensitive context, such as constructing an HTTP response header, the preserved CRLF may alter downstream header parsing.

Affected values may include multipart parameters such as filename, name, or similar parsed header attributes.

Impact

Applications that accept multipart form uploads may be affected if they later reuse parsed multipart metadata in HTTP headers or other header-sensitive contexts.

In affected deployments, an attacker may be able to supply a multipart parameter value containing folded line breaks and cause downstream header injection, response splitting, cache poisoning, or related response parsing issues.

The practical impact depends on application behavior. If parsed multipart metadata is not reused in HTTP headers, the issue may be limited to incorrect parsing behavior rather than a direct exploit path.

Mitigation

Update to a patched version of Rack that removes CRLF correctly when unfolding folded multipart header values.
Avoid copying upload metadata such as filename directly into HTTP response headers without sanitization.
Sanitize or reject carriage return and line feed characters in multipart-derived values before reusing them in response headers, logs, or downstream protocol contexts.
Where feasible, normalize uploaded filenames before storing or reflecting them.

Severity ?

4.8 (Medium)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "RubyGems",
        "name": "rack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.2.0"
            },
            {
              "fixed": "3.2.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-26962"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-93"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-02T20:31:01Z",
    "nvd_published_at": "2026-04-02T18:16:26Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\n`Rack::Multipart::Parser` unfolds folded multipart part headers incorrectly. When a multipart header contains an obs-fold sequence, Rack preserves the embedded CRLF in parsed parameter values such as `filename` or `name` instead of removing the folded line break during unfolding.\n\nAs a result, applications that later reuse those parsed values in HTTP response headers may be vulnerable to downstream header injection or response splitting.\n\n## Details\n\n`Rack::Multipart::Parser` accepts folded multipart header values and unfolds them during parsing. However, the unfolding behavior does not fully remove the embedded line break sequence from the parsed value.\n\nThis means a multipart part header such as:\n\n```http\nContent-Disposition: form-data; name=\"file\"; filename=\"test\\r\\n foo.txt\"\n```\n\ncan result in a parsed parameter value that still contains CRLF characters.\n\nThe issue is not that Rack creates a second multipart header field. Rather, the problem is that CRLF remains embedded in the parsed metadata value after unfolding. If an application later uses that value in a security-sensitive context, such as constructing an HTTP response header, the preserved CRLF may alter downstream header parsing.\n\nAffected values may include multipart parameters such as `filename`, `name`, or similar parsed header attributes.\n\n## Impact\n\nApplications that accept multipart form uploads may be affected if they later reuse parsed multipart metadata in HTTP headers or other header-sensitive contexts.\n\nIn affected deployments, an attacker may be able to supply a multipart parameter value containing folded line breaks and cause downstream header injection, response splitting, cache poisoning, or related response parsing issues.\n\nThe practical impact depends on application behavior. If parsed multipart metadata is not reused in HTTP headers, the issue may be limited to incorrect parsing behavior rather than a direct exploit path.\n\n## Mitigation\n\n* Update to a patched version of Rack that removes CRLF correctly when unfolding folded multipart header values.\n* Avoid copying upload metadata such as `filename` directly into HTTP response headers without sanitization.\n* Sanitize or reject carriage return and line feed characters in multipart-derived values before reusing them in response headers, logs, or downstream protocol contexts.\n* Where feasible, normalize uploaded filenames before storing or reflecting them.",
  "id": "GHSA-rx22-g9mx-qrhv",
  "modified": "2026-04-02T20:31:02Z",
  "published": "2026-04-02T20:31:01Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/rack/rack/security/advisories/GHSA-rx22-g9mx-qrhv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-26962"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/rack/rack"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Rack\u0027s improper unfolding of folded multipart headers preserves CRLF in parsed parameter values"
}

FKIE_CVE-2026-26962

Vulnerability from fkie_nvd - Published: 2026-04-02 18:16 - Updated: 2026-04-21 00:42

Severity ?

4.8 (Medium) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
6.5 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/rack/rack/security/advisories/GHSA-rx22-g9mx-qrhv	Vendor Advisory, Mitigation

Impacted products

	Vendor	Product	Version
	rack	rack	*

JSON

To clipboard

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*",
              "matchCriteriaId": "3FB592AD-E826-49BE-AC6D-E5F55FDCC96E",
              "versionEndExcluding": "3.2.6",
              "versionStartIncluding": "3.2.0",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Rack is a modular Ruby web server interface. From version 3.2.0 to before version 3.2.6, Rack::Multipart::Parser unfolds folded multipart part headers incorrectly. When a multipart header contains an obs-fold sequence, Rack preserves the embedded CRLF in parsed parameter values such as filename or name instead of removing the folded line break during unfolding. As a result, applications that later reuse those parsed values in HTTP response headers may be vulnerable to downstream header injection or response splitting. This issue has been patched in version 3.2.6."
    }
  ],
  "id": "CVE-2026-26962",
  "lastModified": "2026-04-21T00:42:36.393",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 4.8,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 2.5,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      },
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 6.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 2.5,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ]
  },
  "published": "2026-04-02T18:16:26.773",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Vendor Advisory",
        "Mitigation"
      ],
      "url": "https://github.com/rack/rack/security/advisories/GHSA-rx22-g9mx-qrhv"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-93"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

SUSE-SU-2026:1745-1

Vulnerability from csaf_suse - Published: 2026-05-07 07:22 - Updated: 2026-05-07 07:22

Summary

Security update for rmt-server

Severity

Important

Notes

Title of the patch: Security update for rmt-server

Description of the patch: This update for rmt-server fixes the following issues: Update to version 2.27. Security issues fixed: - CVE-2026-26961: rack: greedy multipart boundary parsing can lead to parser differentials and WAF bypass (bsc#1261398). - CVE-2026-26962: rack: improper unfolding of folded multipart headers can lead to downstream header injection and response splitting(bsc#1261471). - CVE-2026-34763: rack: unescaped regex interpolation of configured root path can lead to root directory disclosure (bsc#1261406). - CVE-2026-34785: rack: prefix matching logic can lead to the exposure of unintended files under the static root (bsc#1261417). - CVE-2026-34786: rack: URL-encoded path mismatch can lead to `header_rules` bypass (bsc#1261426). - CVE-2026-34826: rack: missing individual byte range limit checks when parsing HTTP `Range` headers can lead to excessive resource consumption and a denial of service (bsc#1261436). - CVE-2026-34829: rack: multipart parsing without `Content-Length` header can lead to unbounded chunked file uploads and a denial of service (bsc#1261447). - CVE-2026-34230: rack: quadratic complexity when processing of wildcard `Accept-Encoding` headers can lead to a denial of service (bsc#1261388). - CVE-2026-34830: rack: improper sanitization of the `X-Accel-Mapping` request header can lead to the exposure of unintended files via `X-Accel-Redirect` (bsc#1261458). - CVE-2026-34831: rack: `Content-Length` header and body byte size mismatch when creating error responses can lead to incorrect HTTP response framing (bsc#1261466). Other updates and bugfixes: - Fix ReDoS in `Addressable`. - Fix out-of-bounds read in `rdiscount`.

Patchnames: SUSE-2026-1745,SUSE-SLE-Module-Public-Cloud-15-SP7-2026-1745,SUSE-SLE-Module-Server-Applications-15-SP7-2026-1745

CVE-2026-26961

3.7 (Low)


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