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VulnerabilityPublished Updated

CVE-2026-65632: The jose library accepts ECDSA (ES256, ES256K, ES384, and ES512) JWS signatures of a non-canonical

Affects joseSource GCVE Database

0
Authoritative record:CVE-2026-65632· Medium 5.1

Not known to be exploited · CVSS 5.1 Medium.

Data as of 28 Oct 2026, 22:28 UTC

CVSS 4.0 base score
5.1Medium
How severe the flaw is on the 0–10 CVSS scale.
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 26 Oct 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

Affected software

ProductAffectedFixed in
Ubuntu 26.10josepkg:deb/ubuntu/jose?arch=source&distro=stonkingOther threatsAffected
  • =14-2build1
  • =14-2build2
Fixed in–
Ubuntu 26.04 LTSjosepkg:deb/ubuntu/jose?arch=source&distro=resoluteOther threatsAffected
  • =14-2build1
Fixed in–
Ubuntu 24.04 LTSjosepkg:deb/ubuntu/jose?arch=source&distro=nobleOther threatsAffected
  • 11-2 – 13-1
5 affected builds
Fixed in–
Ubuntu 22.04 LTSjosepkg:deb/ubuntu/jose?arch=source&distro=jammyOther threatsAffected
  • =10-3
  • =11-2
Fixed in–
Ubuntu 20.04 LTSjosepkg:deb/ubuntu/jose?arch=source&distro=focalOther threatsAffected
  • =10-2build2
Fixed in–
Ubuntu 18.04 LTSjosepkg:deb/ubuntu/jose?arch=source&distro=bionicOther threatsAffected
  • =10-2
  • =10-2build1
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

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