CVE-2026-44351

Published May 13, 2026

Last updated 4 months ago

CVSS critical 9.1
Jwt

Overview

Description
fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.2.4, a critical authentication-bypass vulnerability in fast-jwt's async key-resolver flow allows any unauthenticated attacker to forge arbitrary JWTs that are accepted as authentic. When the application's key resolver returns an empty string (''), for example via the common keys[decoded.header.kid] || '' JWKS-style fallback, fast-jwt converts it to a zero-length Buffer, hands it to crypto.createSecretKey, derives allowedAlgorithms = ['HS256','HS384','HS512'] from it, and then verifies the token's signature against an empty-key HMAC. The attacker simply computes HMAC-SHA256(key='', input='${header}.${payload}'), which Node accepts without complaint — and the verifier returns the attacker-chosen payload (sub, admin, scopes, etc.) as authentic. This vulnerability is fixed in 6.2.4.
Source
security-advisories@github.com
NVD status
Deferred

Risk scores

CVSS 3.1

Type
Secondary
Base score
9.1
Impact score
5.2
Exploitability score
3.9
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Severity
CRITICAL

Weaknesses

security-advisories@github.com
CWE-287

Social media

Hype score
Not currently trending

Related CVEs

  1. go-base is a Go RESTful API Boilerplate template with JWT Authentication, backed by PostgreSQL. In versions prior to 2026-05-18, the JWT signing secret is hardcoded to the known string "random", letting any attacker who reads the public repository forge tokens for arbitrary users, including admin roles, and completely bypass authentication on all protected endpoints. This value is set in two places: the dev.env template (line 10) and a programmatic fallback in cmd/serve.go (line 35), so the application uses it even when no .env file is present. The original mitigation in auth/jwt/tokenauth.go (lines 22 to 25) only caught the exact string "random", letting other weak secrets through, and replaced it with an in-memory key that was not persisted, invalidating all tokens on every restart and effectively causing a denial-of-service. This issue has been fixed in version 2026-05-18.•CVE-2026-48031
  2. SurrealDB before 3.1.0 silently substitutes the ES384 algorithm when a JWT access method is configured with ALGORITHM ES512 (DEFINE ACCESS ... TYPE JWT ALGORITHM ES512), because the underlying jsonwebtoken crate (v10.x) has no ES512 variant and the mapping defaults to ES384 without any error, warning, or log message. Users who supply the correct P-521 key for ES512 experience authentication handshake failures due to the curve mismatch with ES384 (which expects P-384), and tokens are rejected by external systems expecting genuine ES512 signatures. The flaw cannot be used to forge tokens or compromise data confidentiality or integrity, as ES384 remains cryptographically strong.•CVE-2026-63761
  3. Microsoft SharePoint Weak Authentication Vulnerability•CVE-2026-55040
  4. A flaw was found in Keycloak. This JWT algorithm confusion vulnerability in the JWT Authorization Grant flow allows an attacker with valid client credentials to bypass signature verification. By forging an assertion, the attacker can create unauthorized access tokens. This enables the attacker to impersonate any federated user linked to the affected Identity Provider, leading to unauthorized access and potential privilege escalation.•CVE-2026-11800
  5. A flaw was found in Keycloak. An authenticated user with low privileges can exploit this vulnerability by sending an oversized subject_token JSON Web Token (JWT) to the TokenEndpoint. When the token exceeds a 4000-character limit, it is silently dropped, causing the system to fall back to client credentials. This allows the user to gain the permissions of the client's service account, leading to privilege escalation.•CVE-2026-9704

References

Sources include official advisories and independent security research.