CVE-2026-65632: The jose library accepts ECDSA (ES256, ES256K, ES384, and ES512) JWS signatures of a non-canonical
Source GCVE Database
Not known to be exploited · CVSS 5.1 Medium : upgrade to 1.11.13 when convenient.
Data as of 26 Oct 2026, 22:27 UTC
- Patch
- Available – fixed in 1.11.13, 72ce1866622b9329347dc52a94173ac0317bc9cf
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 26 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade jose to 1.11.13; jose to 72ce1866622b9329347dc52a94173ac0317bc9cf.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| potatosaladjose | Affected
| Fixed in
|
| josepotatosalad/erlang-jose | Affected
| Fixed in
|
Hexjosepkg:hex/joseOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
The jose library accepts ECDSA (ES256, ES256K, ES384, and ES512) JWS signatures of a non-canonical length. When verifying an ECDSA signature, jose_jwk_kty_ec:verify/4 in src/jwk/jose_jwk_kty_ec.erl splits the raw signature in half by its actual byte length (split_binary(Signature, byte_size(Signature) div 2)) instead of enforcing the fixed length required by RFC 7518 §3.4, and then decodes each half with crypto:bytes_to_integer/1, which ignores leading zero bytes. As a result, an attacker who holds one valid token can prepend leading zero bytes to each of the R and S halves to produce longer signatures that still split evenly and decode to the same (r, s) pair, so many distinct signature byte strings all verify against the same key (signature malleability). This does not allow forging new payloads or impersonating a signer, because the underlying (r, s) values are unchanged. It does defeat any security control that assumes a valid token or its signature is unique, such as token-revocation-by-hash, replay or idempotency caches, and deduplication logic. This issue affects jose: from 1.0.0 before 1.11.13.
References
- github.com/potatosalad/erlang-jose/security/advisories/GHSA-44hw-rpw9-mwg4 (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-65632 (opens in a new tab)
- github.com/potatosalad/erlang-jose/commit/72ce1866622b9329347dc52a94173ac0317bc9cf (opens in a new tab)
- github.com/potatosalad/erlang-jose/commit/a7746ecd4950f85a393136e449a91dac62b5c429 (opens in a new tab)
- cna.erlef.org/cves/CVE-2026-65632.html (opens in a new tab)
- osv.dev/vulnerability/EEF-CVE-2026-65632 (opens in a new tab)