The pure-Erlang AES-GCM fallback in jose_jwa_aes derives the number of verified authentication tag bits from the attacker-supplied tag itself. In the {aes_gcm, Bits} clause of block_decrypt/4, the incoming tag is guarded only by is_binary/1, with no check on its length. Verification in gcm_block_decrypt/6 then computes TBits = bit_size(T) and compares only those bits of the real 128-bit tag. An attacker who controls a JWE token can truncate the authentication tag to as little as 8 bits, so only 8 bits are ever checked. This reduces forgery resistance from 2^-128 to 2^-8, and a forged ciphertext is reliably accepted as authentic within 256 attempts without knowledge of the key (an authentication tag forgery and integrity bypass). Supplying a tag longer than 128 bits instead causes a badmatch that crashes the decrypting process. The fallback is reached through the public JWE decryption path whenever AES-GCM is not provided by a native crypto NIF, for example on FIPS or stripped or older OTP builds.
This issue affects jose: from 1.2.0 before 1.11.13.
CVSS
No CVSS.
References
Configurations
No configuration.
History
26 Oct 2026, 20:17
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-10-26 20:17
Updated : 2026-10-27 15:00
NVD link : CVE-2026-65625
Mitre link : CVE-2026-65625
CVE.ORG link : CVE-2026-65625
JSON object : View
Products Affected
No product.
CWE
CWE-354
Improper Validation of Integrity Check Value