Vulnerability-Lookup

CVE-2026-119284 (GCVE-0-2026-119284)

Vulnerability from cvelistv5 – Published: 2026-10-29 21:33 – Updated: 2026-10-30 17:05

Title

joserfc: Compact JWS size guard allocates attacker-controlled segments before rejection

Summary

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.7.6, joserfc compact JWS deserialization calls bytes.split() before enforcing the existing aggregate segment-size limits. When attacker-controlled compact serialization bytes reach deserialize_compact(), the split creates copies of the header, payload, and signature segments before ExceededSizeError rejects them, causing an additional allocation approximately proportional to the supplied token. Requests that exhaust available process memory can therefore cause an availability failure even though signature verification fails. This issue is fixed in version 1.7.6.

Severity

6.9 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-30 17:05 UTC

CWE

CWE-400 - Uncontrolled Resource Consumption

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 8053 records in the last 180 days details

References

3 references

URL	Tags
https://github.com/authlib/joserfc/security/advis…	x_refsource_CONFIRM
https://github.com/authlib/joserfc/commit/397e04f…	x_refsource_MISC
https://github.com/authlib/joserfc/releases/tag/1.7.6	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
authlib	joserfc	Affected: < 1.7.6	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-119284

Vulnerability from fkie_nvd - Published: 2026-10-29 22:17 - Updated: 2026-10-30 17:17

Severity

6.9 (Medium) - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/authlib/joserfc/commit/397e04f4bbce0b94d86e31c1c003f4640af8fb39
	security-advisories@github.com	https://github.com/authlib/joserfc/releases/tag/1.7.6
	security-advisories@github.com	https://github.com/authlib/joserfc/security/advisories/GHSA-9pg5-8c7x-5hfx
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/authlib/joserfc/security/advisories/GHSA-9pg5-8c7x-5hfx

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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      "affectedData": [
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          "product": "joserfc",
          "vendor": "authlib",
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    }
  ],
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  "lastModified": "2026-10-30T17:17:17.850",
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GHSA-9PG5-8C7X-5HFX

Vulnerability from github – Published: 2026-10-30 14:54 – Updated: 2026-10-30 14:54

Summary

joserfc: Compact JWS size guard allocates attacker-controlled segments before rejection

Details

Summary

joserfc 1.7.4 defines compact-JWS header, payload, and signature limits, but calls value.split(b".") before validating them. Python bytes.split() copies the attacker-controlled segments, so the current guard allocates roughly one complete payload before rejecting it.

Reproduction

.venv-research/bin/python 06-practical-testing/preauth-memory-profile.py

The input is resident before a fork-isolated verifier runs, and every signature is invalid.

Input	Peak RSS delta	Amplification	Result
1 MiB	1.11 MiB	1.11×	size rejected
4 MiB	4.04 MiB	1.01×	size rejected
8 MiB	8.04 MiB	1.01×	size rejected
16 MiB	16.04 MiB	1.00×	size rejected
32 MiB	31.74 MiB	0.99×	size rejected
64 MiB	63.80 MiB	1.00×	size rejected

The unconstrained profile is the primary evidence: joserfc allocates an additional attacker-sized object before producing its intended ExceededSizeError. A separate baseline-plus-headroom stress test raises MemoryError when that copy cannot fit, but this report does not characterize an absolute RLIMIT_AS value as a realistic worker memory budget.

Security Argument

The issue is not that joserfc can prevent the transport layer from receiving a large header. The issue is narrower: once bytes reach deserialize_compact(), the library's existing size guard cannot fulfill its allocation-limiting purpose because attacker-controlled segment copies are created first.

This differs from GHSA-frfh-8v73-gjg4, which concerned embedding already-loaded oversized segments in exception and log messages. Here, the current implementation itself creates an additional payload-sized allocation before its fixed size exception.

Recommended Fix

Check len(value) against a maximum compact-serialization size before split(). If per-segment diagnostics are needed, locate delimiters with bounded find() operations or memory views, validate offsets and lengths, and only then materialize acceptable segments.

Severity

6.9 (Medium)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "joserfc"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.7.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-119284"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-30T14:54:25Z",
    "nvd_published_at": "2026-10-29T22:17:01Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\njoserfc 1.7.4 defines compact-JWS header, payload, and signature limits, but\ncalls `value.split(b\".\")` before validating them. Python `bytes.split()` copies\nthe attacker-controlled segments, so the current guard allocates roughly one\ncomplete payload before rejecting it.\n\n## Reproduction\n\n```bash\n.venv-research/bin/python 06-practical-testing/preauth-memory-profile.py\n```\n\nThe input is resident before a fork-isolated verifier runs, and every signature\nis invalid.\n\n| Input | Peak RSS delta | Amplification | Result |\n|---:|---:|---:|---|\n| 1 MiB | 1.11 MiB | 1.11\u00d7 | size rejected |\n| 4 MiB | 4.04 MiB | 1.01\u00d7 | size rejected |\n| 8 MiB | 8.04 MiB | 1.01\u00d7 | size rejected |\n| 16 MiB | 16.04 MiB | 1.00\u00d7 | size rejected |\n| 32 MiB | 31.74 MiB | 0.99\u00d7 | size rejected |\n| 64 MiB | 63.80 MiB | 1.00\u00d7 | size rejected |\n\nThe unconstrained profile is the primary evidence: joserfc allocates an\nadditional attacker-sized object before producing its intended\n`ExceededSizeError`. A separate baseline-plus-headroom stress test raises\n`MemoryError` when that copy cannot fit, but this report does not characterize\nan absolute `RLIMIT_AS` value as a realistic worker memory budget.\n\n## Security Argument\n\nThe issue is not that joserfc can prevent the transport layer from receiving a\nlarge header. The issue is narrower: once bytes reach `deserialize_compact()`,\nthe library\u0027s existing size guard cannot fulfill its allocation-limiting purpose\nbecause attacker-controlled segment copies are created first.\n\nThis differs from\n[GHSA-frfh-8v73-gjg4](https://github.com/authlib/joserfc/security/advisories/GHSA-frfh-8v73-gjg4),\nwhich concerned embedding already-loaded oversized segments in exception and log\nmessages. Here, the current implementation itself creates an additional\npayload-sized allocation before its fixed size exception.\n\n## Recommended Fix\n\nCheck `len(value)` against a maximum compact-serialization size before\n`split()`. If per-segment diagnostics are needed, locate delimiters with bounded\n`find()` operations or memory views, validate offsets and lengths, and only then\nmaterialize acceptable segments.",
  "id": "GHSA-9pg5-8c7x-5hfx",
  "modified": "2026-10-30T14:54:25Z",
  "published": "2026-10-30T14:54:25Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/authlib/joserfc/security/advisories/GHSA-9pg5-8c7x-5hfx"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-119284"
    },
    {
      "type": "WEB",
      "url": "https://github.com/authlib/joserfc/commit/397e04f4bbce0b94d86e31c1c003f4640af8fb39"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/authlib/joserfc"
    },
    {
      "type": "WEB",
      "url": "https://github.com/authlib/joserfc/releases/tag/1.7.6"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "joserfc: Compact JWS size guard allocates attacker-controlled segments before rejection"
}

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CVE-2026-119284 (GCVE-0-2026-119284)

FKIE_CVE-2026-119284

GHSA-9PG5-8C7X-5HFX

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