CVE Intelligence
Medium Cryptography

CVE-2026-65632 — ECDSA signature length is not validated in jose, allowing signature malleability

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.

Published Oct 26, 2026 · Updated Oct 26, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: EEF

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
—
No EPSS score.
Affects
Potatosalad
Jose
CVSS base
5.1
Medium · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Potatosalad Jose).
  2. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  3. Search available logs for exploit probes matching the vulnerability class (cryptography), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Potatosalad Jose ≥ 1.0.0 and < 1.11.13≥ a7746ecd4950f85a393136e449a91dac62b5c429 and < 72ce1866622b9329347dc52a94173ac0317bc9cf Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Local
Attack complexity
Low
Attack requirements
None
Privileges required
None
User interaction
None
Scope
X
Confidentiality (vulnerable system)
None
Integrity (vulnerable system)
Low
Availability (vulnerable system)
None
Confidentiality (subsequent)
None
Integrity (subsequent)
None
Availability (subsequent)
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
5.1 CVSS 4.0 Medium — — 6b3ad84c-e1a6-4bf7-a703-f496b71e49db via NIST National Vulnerability Database
5.1 CVSS 4.0 Medium — — EEF via CVE Program (cve.org) e CISA ADP
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X (score shown at the top: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-347 · Improper Verification of Cryptographic Signature

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
  • Check TLS negotiations and unexpected certificates in the component’s traffic.
endpoint telemetry (EDR)network IDS/IPS

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · potatosalad/jose
    Oct 26, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 26, 2026
  • CVSS changed · 5.1
    Oct 26, 2026 · NIST National Vulnerability Database
  • Source status changed · → Received
    Oct 26, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 26, 2026 · Alertas do Telegram
  • CVE published
    Oct 26, 2026 · EEF

Source activity

Repeated readings are counted rather than listed.

  • 1× References added · Oct 26, 2026 – Oct 26, 2026
  • 1× Official description updated · Oct 26, 2026 – Oct 26, 2026

References

5 on the record

Elsewhere on this site

Potatosalad
every CVE for this vendor
Cryptography
same class
CWE-347
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-65626 Bleichenbacher padding oracle in RSAES-PKCS1-v1_5 decryption in jose 11h
  • CVE-2026-65627 Decompression bomb via unbounded zlib:inflate in jose_jwe_zip:uncompress/2 11h
  • CVE-2026-65628 Infinite recursion (CPU denial-of-service) in JOSE.JWK.shared_secret/2 on mismatched key types 11h
  • CVE-2026-65629 Weak PBKDF2 parameters for password-encrypted private-key export in jose 11h
  • CVE-2026-65631 erlang-jose RSA JWK parsing attempts to factor an attacker-controlled modulus, enabling CPU-exhaustion denial of service 11h
  • CVE-2026-65630 Timing side-channel in pure-Erlang X25519 scalar multiplication leaks the private key in jose 11h

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No FIRST EPSS score.
  • No fixed version, patch or mitigation documented.
  • No CISA SSVC assessment.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-65632 is "ECDSA signature length is not validated in jose, allowing signature malleability", rated Medium. It affects Jose (Potatosalad); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.1 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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