Vulnerability in PyJWT (CVE-2026-102269)
Summary
Vulnerability in PyJWT (CVE-2026-102269). Risk of unauthorized operations or information disclosure. Exploitable via jti. Mitigation: upgrade to 2.14.0 or later.
Original description
The description as published by the source.
Summary
PyJWT 2.13.0 accepts compact JWS signature segments containing characters that
are not in the Base64URL alphabet. Appending !!!! to a valid signature does
not change the decoded signature bytes or authenticated claims, but it changes
the serialized token and its SHA-256 hash. An application that indexes logout
or revocation state by the raw token therefore rejects the logged-out token and
accepts its no-key alternate serialization.
This report separates two issues: permissive compact-JWS decoding is the
library behavior, while using raw serialized JWT text as a security identity is
a dangerous application composition. A jti-indexed control blocks both
representations.
Affected Version
Confirmed with PyJWT 2.13.0 on CPython 3.13. The mutation changes only the
signature segment and requires no signing key.
End-to-End Reproduction
.venv-research/bin/python 06-practical-testing/revocation-bypass-lab.py
The loopback-only lab performs:
- Issue a valid HS256 admin token.
- Access
/protectedsuccessfully. - Log out the canonical token and store
SHA256(raw_token). - Confirm canonical replay returns HTTP 401.
- Append
!!!!to only the signature segment. - Confirm the mutated token has the same verified claims and signature bytes,
a different raw hash, and receives HTTP 200. - Repeat with
jti-indexed revocation and confirm both forms return HTTP 401.
Observed statuses for raw-token revocation were 200 -> logout -> 401 for the…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-102269 has been found in PyJWT.
Attackers can target a specific entry point like jti over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 4.8/10.
What to do: upgrade PyJWT to 2.14.0 or later.
If unsure, ask your IT team or search "PyJWT CVE-2026-102269" on the vendor's site.
CVE-2026-102269 (PyJWT) — CWE-180 / CVSS v3 4.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: jti / master / e6f48401001609a8f99e71fcaf355fb895d508a8
Patched: 2.14.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-180) exists in PyJWT. Attackers reach the vulnerable code path via jti without authentication.
Check the vendor advisory for the affected versions of PyJWT. Attack surface: jti / master / e6f48401001609a8f99e71fcaf355fb895d508a8.
Severity: Medium (CVSS 4.8/10). Risk of unauthorized operations or information disclosure.
Update to 2.14.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'PyJWT' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'PyJWT' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
PyJWTを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade PyJWT to 2.14.0ステージング環境で 2.14.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- package pypi.org
- web github.com
- web github.com
- web github.com