Description
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.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
potatosalad jose
Default version status: unaffected
1.2.0 to < 1.11.13affected
pkg:hex/josepotatosalad jose
Default version status: unaffected
8848b172575fb7d7e1e2977e8ae0a21678d2157a to < 3fa1f8e3efda0da5ce6f4c9984789f979dc02740affected
pkg:github/potatosalad/erlang-joseReferences
- https://github.com/potatosalad/erlang-jose/security/advisories/GHSA-6gxw-6f7r-cjr6 ↗
- https://cna.erlef.org/cves/CVE-2026-65625.html ↗
- https://osv.dev/vulnerability/EEF-CVE-2026-65625 ↗
- https://github.com/potatosalad/erlang-jose/commit/8848b172575fb7d7e1e2977e8ae0a21678d2157a ↗
- https://github.com/potatosalad/erlang-jose/commit/3fa1f8e3efda0da5ce6f4c9984789f979dc02740 ↗