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CVE-2026-48522 medium CVSS 4.2

Vulnerability in pyjwt (CVE-2026-48522)

Summary

Vulnerability in pyjwt (CVE-2026-48522). Risk of unauthorized operations or information disclosure. Exploitable via uri. Mitigation: upgrade to 2.13.0 or later.

Original description

The description as published by the source.

[!NOTE]
The library does not directly return non-HTTP(S) URI contents to the attacker; the chained "plant a JWKS to forge tokens" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. Severity is scored for the scheme-acceptance bug in isolation.

Summary

PyJWKClient passes its uri argument directly to urllib.request.urlopen() which uses Python stdlib's default OpenerDirector registering HTTPHandler, HTTPSHandler, FTPHandler, FileHandler, and DataHandler. There is currently no documented option to restrict which schemes PyJWKClient will fetch.

If an application's jku URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can:

  1. Cause PyJWKClient to read arbitrary local files via file:// (SSRF on local filesystem) — the file's contents are passed to json.load.
  2. Cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface).
  3. Forge tokens that PyJWT verifies as valid — if the attacker can write to any path the JKU URL points at AND influences the URL, they can plant a JWK Set containing their own public key, sign tokens with the matching private key, and jwt.decode() accepts.

Affected versions

Tested and reproducible on PyJWT 2.11.0 and 2.12.1. Likely all versions back to PyJWKClient introduction.

R…

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-2026-48522 has been found in pyjwt.
Attackers can target a specific entry point like uri over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 4.2/10.
What to do: upgrade pyjwt to 2.13.0 or later.
If unsure, ask your IT team or search "pyjwt CVE-2026-48522" on the vendor's site.

CVE-2026-48522 (pyjwt) — CWE-441 / CVSS v3 4.2
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: uri / OpenerDirector / HTTPHandler / HTTPSHandler
Patched: 2.13.0 — 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-441) exists in pyjwt. Attackers reach the vulnerable code path via uri without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of pyjwt. Attack surface: uri / OpenerDirector / HTTPHandler / HTTPSHandler.

🔥 Severity

Severity: Medium (CVSS 4.2/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 2.13.0.

🛡️ 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 2.13.0

    ステージング環境で 2.13.0 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":"2.13.0"}]}]
pip PyJWT
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.13.0"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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