CVE Intelligence
Medium

CVE-2026-65625 — Attacker-controlled AES-GCM authentication tag length allows tag forgery in jose

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.

Published Oct 26, 2026 · Updated Oct 27, 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
  • EPSS 0.1% (30-day exploitation probability)+0
  • 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
0.12%
ahead of 2% of scored CVEs · Oct 27, 2026
Affects
Potatosalad
Jose
CVSS base
5.9
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, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Potatosalad Jose ≥ 1.2.0 and < 1.11.13≥ 8848b172575fb7d7e1e2977e8ae0a21678d2157a and < 3fa1f8e3efda0da5ce6f4c9984789f979dc02740 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
Present
Privileges required
None
User interaction
None
Scope
X
Confidentiality (vulnerable system)
None
Integrity (vulnerable system)
High
Availability (vulnerable system)
Low
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
5.9 CVSS 4.0 Medium — — 6b3ad84c-e1a6-4bf7-a703-f496b71e49db via NIST National Vulnerability Database
5.9 CVSS 4.0 Medium — — EEF via CVE Program (cve.org) e CISA ADP
CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:L/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-354

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.
endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

  • 2026
  • Source status changed · Received → Deferred
    Oct 27, 2026 · NIST National Vulnerability Database
  • Affected products added · potatosalad/jose
    Oct 26, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 26, 2026
  • CVSS changed · 5.9
    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
CWE-354
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-65632 ECDSA signature length is not validated in jose, allowing signature malleability 1d
  • CVE-2026-65626 Bleichenbacher padding oracle in RSAES-PKCS1-v1_5 decryption in jose 1d
  • CVE-2026-65627 Decompression bomb via unbounded zlib:inflate in jose_jwe_zip:uncompress/2 1d
  • CVE-2026-65628 Infinite recursion (CPU denial-of-service) in JOSE.JWK.shared_secret/2 on mismatched key types 1d
  • CVE-2026-65629 Weak PBKDF2 parameters for password-encrypted private-key export in jose 1d
  • CVE-2026-65631 erlang-jose RSA JWK parsing attempts to factor an attacker-controlled modulus, enabling CPU-exhaustion denial of service 1d

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 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-2026-65625 is "Attacker-controlled AES-GCM authentication tag length allows tag forgery in jose", 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 5.9 describes technical severity. EPSS 0.12% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

Comments

Moderated technical discussion. Read the community guidelines.

No comments yet.

Sign in or create an account to comment and suggest corrections.