CVE-2026-65626 potatosalad CVE debrief

Who should care

Defenders of systems using the affected jose versions should assess their exposure and prioritize verifying the impact of this vulnerability. This includes operators, platform administrators, vulnerability management teams, and security teams who need to verify if the affected jose versions are used in their environment and apply patches or mitigations accordingly.

Why it matters

CVE-2026-65626 is a Bleichenbacher padding oracle vulnerability in the jose_jwa_pkcs1 module that allows unauthenticated attackers to recover plaintext or forge signatures. Defenders should prioritize verifying exposure and assessing the impact on their systems, especially those using affected jose versions.

• Recovery of plaintext of intercepted ciphertexts
• Forgery of signatures through adaptive chosen-ciphertext queries
• Potential for attackers to access sensitive information
• Need for verification of exposure and impact on systems

Technical summary

The pure-Erlang RSAES-PKCS1-v1_5 decryption in the jose_jwa_pkcs1 module is a Bleichenbacher padding oracle. This allows an unauthenticated attacker who knows only the public RSA key to recover the plaintext of intercepted ciphertexts or forge signatures through roughly 10^4 to 10^6 adaptive chosen-ciphertext queries. The vulnerability is caused by the lack of an implicit-rejection countermeasure in the jose_jwa_pkcs1 module, which allows a padding oracle attack. The attack can be performed by submitting ciphertexts to a decryption endpoint that unwraps RSA1_5 JWE keys. Affected product deployments should be verified, and owners should assess their exposure and prioritize verifying the impact of this on their

Defensive priority

Defenders should prioritize verifying exposure and assessing the impact of this vulnerability on their systems, especially those using the affected jose versions.

Recommended defensive actions

• Verify if the affected jose versions are used in the environment
• Assess the impact of the vulnerability on the systems
• Apply the patch or upgrade to a fixed version of jose
• Monitor for potential attacks using adaptive chosen-ciphertext queries
• 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.

Evidence notes

The vulnerability is caused by the lack of an implicit-rejection countermeasure in the jose_jwa_pkcs1 module, which allows a padding oracle attack. The attack can be performed by submitting ciphertexts to a decryption endpoint that unwraps RSA1_5 JWE keys.

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.