Goal Reached Thanks to every supporter — we hit 100%!

Goal: 1000 CNY · Raised: 1359 CNY

100%
Buy Us a Coffee

CVE-2026-107723— fast-jwt : Silent claim-validator bypass when JWT payload is a JSON array

Quick assessment

Affected
nearform fast-jwt
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

fast-jwt 提供了快速实现 JSON Web Token（JWT）的库。在版本 6.3.0 之前，fast-jwt 的 函数会接受负载（payload）为 JSON 数组且签名有效的 JWT。这是因为在 中，代码仅检查负载是否为对象（object），但未拒绝数组（array）。由于 JSON 数组不包含名为 、 、 、 、 、 或 的声明（claims），声明验证循环找不到这些属性，从而静默跳过所有相关的配置验证，并直接将数组作为验证成功的负载返回。 攻击者若能构造或影响一个签名有效的令牌，即可绕过令牌过期时

CVSS 8.1 · High

Possible ATT&CK Techniques 1 AI

T1136.003 · Cloud Account
Get alerts for future matching vulnerabilities Log in to subscribe

I. Basic Information for CVE-2026-107723

Vulnerability Information
Have questions about the vulnerability? See if Shenlong's analysis helps!
View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
fast-jwt : Silent claim-validator bypass when JWT payload is a JSON array
Source: CVE Program / CVE List V5
Vulnerability Description
fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.0, fast-jwt createVerifier accepts a validly signed JWT whose payload is a JSON array because src/decoder.js checks that the payload is an object but does not reject arrays. The claim validator loop then finds no named exp, nbf, iss, aud, sub, jti, or nonce properties and silently skips those configured checks, returning the array as a successfully verified payload. An attacker who can produce or influence a validly signed token may bypass expiry, issuer, audience, subject, revocation, and replay protections. The opt-in requiredClaims option can block missing claims, and signature verification itself is not bypassed. This issue is fixed in version 6.3.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1287
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
nearform fast-jwt < 6.3.0 -

II. Public POCs for CVE-2026-107723

# POC Description Source Link Shenlong Link
AI-Generated POC Premium

No public POC found.

Login to generate AI POC

III. Intelligence Information for CVE-2026-107723

请登录查看更多情报信息。

Patches & Fixes for CVE-2026-107723 (2)

Vendor Advisories for CVE-2026-107723 (1)

Vendor Pages for CVE-2026-107723 (1)

Same Patch Batch · nearform · 2026-10-08 · 6 CVEs total

CVE-2026-107722 9.8 CRITICAL fast-jwt: Incomplete patch of CVE-2026-34950: Non-whitespace key-prefix re-enables RSA→HS2
CVE-2026-107720 7.4 HIGH fast-jwt: createVerifier accepts unsigned JWTs when key is '' or null and algorithms is ex
CVE-2026-107724 7.4 HIGH fast-jwt treats raw public JWK JSON as an HMAC secret, enabling HS256 token forgery
CVE-2026-107721 5.9 MEDIUM fast-jwt clockTolerance: Infinity silently bypasses both exp and nbf validation (and persi
CVE-2026-107719 4.2 MEDIUM fast-jwt: Verifier cache accepts expired JWTs without iat.

IV. Related Vulnerabilities

Same product: fast-jwt
Same vendor: nearform
Same weakness: CWE-1287

V. Comments for CVE-2026-107723

No comments yet

Leave a comment