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CVE-2026-32597 high CVSS 7.5

Vulnerability in pyjwt (CVE-2026-32597)

Summary

Vulnerability in pyjwt (CVE-2026-32597). Data can be tampered with by attackers. Exploitable via crit. Mitigation: upgrade to 2.12.0 or later.

Original description

The description as published by the source.

Summary

PyJWT does not validate the crit (Critical) Header Parameter defined in
RFC 7515 §4.1.11. When a JWS token contains a crit array listing
extensions that PyJWT does not understand, the library accepts the token
instead of rejecting it. This violates the MUST requirement in the RFC.

This is the same class of vulnerability as CVE-2025-59420 (Authlib),
which received CVSS 7.5 (HIGH).

RFC Requirement

RFC 7515 §4.1.11:

The "crit" (Critical) Header Parameter indicates that extensions to this
specification and/or [JWA] are being used that MUST be understood and
processed. [...] If any of the listed extension Header Parameters are
not understood and supported by the recipient, then the JWS is invalid.

Proof of Concept

import jwt  # PyJWT 2.8.0
import hmac, hashlib, base64, json

# Construct token with unknown critical extension
header = {"alg": "HS256", "crit": ["x-custom-policy"], "x-custom-policy": "require-mfa"}
payload = {"sub": "attacker", "role": "admin"}

def b64url(data):
    return base64.urlsafe_b64encode(data).rstrip(b"=").decode()

h = b64url(json.dumps(header, separators=(",", ":")).encode())
p = b64url(json.dumps(payload, separators=(",", ":")).encode())
sig = b64url(hmac.new(b"secret", f"{h}.{p}".encode(), hashlib.sha256).digest())
token = f"{h}.{p}.{sig}"

# Should REJECT — x-custom-policy is not understood by PyJWT
try:
    result = jwt.decode(token, "secret", algorithms=["HS256"])
    print(f"ACC…

Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV

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-2026-32597 has been found in pyjwt.
Attackers can target a specific entry point like crit over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 7.5/10.
What to do: upgrade pyjwt to 2.12.0 or later.
If unsure, ask your IT team or search "pyjwt CVE-2026-32597" on the vendor's site.

CVE-2026-32597 (pyjwt) — CWE-345 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: crit / cnf
Patched: 2.12.0 — 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.

❓ What is the problem

A vulnerability (CWE-345) exists in pyjwt. Attackers reach the vulnerable code path via crit without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of pyjwt. Attack surface: crit / cnf.

🔥 Severity

Severity: High (CVSS 7.5/10). Data can be tampered with by attackers.

🔧 How to fix

Update to 2.12.0.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

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

  1. 1
    Identify 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。

  2. 2
    Apply patch patch 
    Upgrade pyjwt to 2.12.0

    ステージング環境で 2.12.0 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。

  3. 3
    Post-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

PyPI pyjwt
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.12.0"}]}]
pip PyJWT
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.12.0"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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