Sign in Sign up
JA · EN · FR
SecPulse
Categories
CVE-2026-48526 high CVSS 7.4

Authentication Bypass in pyjwt (CVE-2026-48526)

Summary

Authentication bypass in pyjwt (CVE-2026-48526). Confidential information can be exposed externally. Mitigation: upgrade to 2.13.0 or later.

Original description

The description as published by the source.

[!NOTE]
Exploitation requires a verifier configured with both symmetric and asymmetric algorithms in algorithms=[…] and a raw-JSON JWK as the key= argument, both contrary to documented usage, hence the High attack-complexity rating.

Summary

When the verifier is decoding JSON Web Tokens, while supporting both asymmetric and HMAC algorithms, the library does not validate use of JSON Web Keys in HMAC algorithm, allowing attacker to use the issuer public key as the secret key for HMAC algorithm.

Details

In JWT algorithm confusion attack, the verifier is mistakenly use of public key to be used as the shared secret in symmetric algorithms.
In pyjwt case, when the verifier is supporting both HMAC with other asymmetric algorithm and mistakenly using the public key of the issuer to verify the token as demonstrated in the following example:

jws.decode(token, key=rsa_jwk_json, algorithms=["HS256","RS256"]))

An attacker who specifies in the token header to use HMAC, will cause the verifier to accept the JWK as the secret key in HMAC algorithm.
The attacker will be able to forge JWT signed with the public key of the issuer to impersonate any user.

If we look on current protections implemented in the library, at class HMACAlgorithm:

  def prepare_key(self, key: str | bytes) -> bytes:
        key_bytes = force_bytes(key)

        if is_pem_format(key_bytes) or is_ssh_key(key_bytes):
            raise InvalidKeyError(
                "The specified key is…

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-2026-48526 has been found in pyjwt.
Confidential information can be exposed externally. CVSS score: 7.4/10.
What to do: upgrade pyjwt to 2.13.0 or later.
If unsure, ask your IT team or search "pyjwt CVE-2026-48526" on the vendor's site.

CVE-2026-48526 (pyjwt) — CWE-287 / CVSS v3 7.4
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
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

Authentication bypass (CWE-287) exists in pyjwt.

📍 Affected scope

Check the vendor advisory for the affected versions of pyjwt.

🔥 Severity

Severity: High (CVSS 7.4/10). Confidential information can be exposed externally.

🔧 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

We use cookies for analytics and ad measurement. This setting applies to all Game co., Ltd. sites. Details