The Omnivore API (packages/api) before the fix in commit abf53d6 contains an authentication bypass in Apple sign-in token verification. The decodeAppleToken function extracted the 'alg' field from the attacker-supplied JWT header and passed it as the sole allowed algorithm to jwt.verify(). Using jsonwebtoken v8 (which does not validate key/algorithm compatibility), an attacker can set alg=HS256 and sign a forged token using Apple's publicly available RSA public key as the HMAC secret, bypassing signature verification and impersonating any Apple-linked account.
https://github.com/omnivore-app/omnivore/pull/4652
https://github.com/omnivore-app/omnivore/commit/abf53d6508755d3d22a994e28e370a9193ea977a
Published: 2026-08-29
Updated: 2026-08-29
Base Score: 9.4
Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:N
Severity: High
Base Score: 9.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Severity: Critical
Base Score: 9.3
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Severity: Critical