Vulnerability in LibJWT (CVE-2026-44699)
Summary
Vulnerability in LibJWT (CVE-2026-44699). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 3.3.3 or later.
Original description
The description as published by the source.
LibJWT is a C JSON Web Token Library. From 3.0.0 to 3.3.2, libjwt accepts an RSA JWK that does not contain an alg parameter as the verification key for an HS256/HS384/HS512 token. In the OpenSSL backend, this causes HMAC verification to run with a zero-length key, so an attacker can forge a valid JWT without knowing any secret or RSA private key. This is an algorithm-confusion authentication bypass. It affects applications that load RSA keys from JWKS where alg is omitted, which is valid JWK syntax and common in real deployments, and then choose the verification algorithm from the JWT header, for example in a kid lookup callback. This vulnerability is fixed in 3.3.3.
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-2026-44699 has been found in LibJWT.
Risk of unauthorized operations or information disclosure.
What to do: upgrade LibJWT to 3.3.3 or later.
If unsure, ask your IT team or search "LibJWT CVE-2026-44699" on the vendor's site.
CVE-2026-44699 (LibJWT) — CWE-327
Patched: 3.3.3 — 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-327) exists in LibJWT.
Check the vendor advisory for the affected versions of LibJWT.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 3.3.3.
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 'LibJWT' . 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
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1Identify exposure identify
grep -r 'LibJWT' . | 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
LibJWT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 LibJWT to 3.3.3ステージング環境で 3.3.3 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。
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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。
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-44699 libjwt3 Fixed in: 3.3.3-1
- Ubuntu UBUNTU-CVE-2026-44699 libjwt
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov