CVE-2026-65625 potatosalad CVE debrief

Who should care

Defenders who use jose versions from 1.2.0 before 1.11.13 should verify the authenticity of JWE tokens and ensure the integrity of the decryption process. This includes operators, platform administrators, vulnerability management teams, and security teams who need to assess the impact of this vulnerability on their systems and take appropriate measures to mitigate it.

Why it matters

CVE-2026-65625 is a vulnerability in the pure-Erlang AES-GCM fallback in jose_jwa_aes that allows an attacker to truncate the authentication tag, reducing forgery resistance. Defenders should prioritize verifying the authenticity of JWE tokens and ensuring the integrity of the decryption process.

• An attacker can forge ciphertext and have it reliably accepted as authentic within 256 attempts without knowledge of the key.
• The decryption process can be crashed by supplying a tag longer than 128 bits.
• Defenders need to verify the authenticity of JWE tokens and ensure the integrity of the decryption process.
• The vulnerability requires verification of the affected versions and remediation priority.

Technical summary

The pure-Erlang AES-GCM fallback in jose_jwa_aes derives the number of verified authentication tag bits from the attacker-supplied tag itself. This allows an attacker to truncate the authentication tag to as little as 8 bits, reducing forgery resistance from 2^-128 to 2^-8. The vulnerability affects jose versions from 1.2.0 before 1.11.13. The fallback is reached through the public JWE decryption path whenever AES-GCM is not provided by a native crypto NIF. 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.

Defensive priority

Defenders should prioritize verifying the authenticity of JWE tokens and ensuring the integrity of the decryption process.

Recommended defensive actions

• Verify the authenticity of JWE tokens
• Ensure the integrity of the decryption process
• Update jose to version 1.11.13 or later
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability is caused by the pure-Erlang AES-GCM fallback in jose_jwa_aes deriving the number of verified authentication tag bits from the attacker-supplied tag itself. The fallback is reached through the public JWE decryption path whenever AES-GCM is not provided by a native crypto NIF.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.