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GHSA-95C6-P277-P87G

Vulnerability from github – Published: 2026-01-21 22:27 – Updated: 2026-01-22 15:40
VLAI
Summary
FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection
Details

Impact

Timing side-channel vulnerability in verify_key(). The method applied a random delay only on verification failures, allowing an attacker to statistically distinguish valid from invalid API keys by measuring response latencies. With enough repeated requests, an adversary could infer whether a key_id corresponds to a valid key, potentially accelerating brute-force or enumeration attacks.

Affected: all users relying on verify_key() for API key authentication prior to the fix.

Patches

Yes. Users should upgrade to version 1.1.0 (or the version containing this fix). The patch applies a uniform random delay (min_delay to max_delay) to all responses regardless of outcome, eliminating the timing correlation.

Workarounds

  • Add an application-level fixed delay or random jitter to all authentication responses (success and failure) before the fix is applied.
  • Use rate limiting to reduce the feasibility of statistical timing attacks.

References

  • CWE-208: Observable Timing Discrepancy
  • Commit: 87b27640f77c5ef86c46311b6b5a7e2887e35b77
  • OWASP: https://owasp.org/www-community/attacks/Timing_attack
Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "fastapi-api-key"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.1.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-23996"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-208"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-01-21T22:27:39Z",
    "nvd_published_at": "2026-01-21T23:15:53Z",
    "severity": "LOW"
  },
  "details": "### Impact\nTiming side-channel vulnerability in verify_key(). The method applied a random delay only on verification failures, allowing an attacker to statistically distinguish valid from invalid API keys by measuring response latencies. With enough repeated requests, an adversary could infer whether a key_id corresponds to a valid key, potentially accelerating brute-force or enumeration attacks.\n\nAffected: all users relying on verify_key() for API key authentication prior to the fix.\n\n### Patches\nYes. Users should upgrade to version 1.1.0 (or the version containing this fix). The patch applies a uniform random delay (min_delay to max_delay) to all responses regardless of outcome, eliminating the timing correlation.\n\n### Workarounds\n- Add an application-level fixed delay or random jitter to all authentication responses (success and failure) before the fix is applied.\n- Use rate limiting to reduce the feasibility of statistical timing attacks.\n\n### References\n- CWE-208: Observable Timing Discrepancy\n- Commit: 87b27640f77c5ef86c46311b6b5a7e2887e35b77\n- OWASP: https://owasp.org/www-community/attacks/Timing_attack",
  "id": "GHSA-95c6-p277-p87g",
  "modified": "2026-01-22T15:40:29Z",
  "published": "2026-01-21T22:27:39Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Athroniaeth/fastapi-api-key/security/advisories/GHSA-95c6-p277-p87g"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23996"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Athroniaeth/fastapi-api-key/commit/310b2c5c77305f38c63c0b917539a0344071dfd8"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Athroniaeth/fastapi-api-key"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Athroniaeth/fastapi-api-key/releases/tag/1.1.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection"
}



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