CVE-2026-75803 OpenSSL CVE debrief

Who should care

Defenders responsible for OpenSSL deployments, developers using EVP_Cipher() with AEAD ciphers, security teams assessing vulnerability impact and remediation, and operators managing affected platforms should prioritize verification, updating, and code reviews to mitigate this risk.

Why it matters

This vulnerability in OpenSSL's EVP_Cipher() function can lead to the acceptance of forged messages, impacting applications relying on AEAD ciphers for secure communication. Defenders should prioritize verification, updating, and code reviews to mitigate this risk.

• Potential acceptance of forged messages due to improper AEAD tag validation
• Need for verification and update of OpenSSL to non-vulnerable versions
• Review and adjustment of application code using EVP_Cipher() with AEAD ciphers

Technical summary

The EVP_Cipher() API call in OpenSSL does not verify AEAD tags for empty ciphertexts with ChaCha20-Poly1305 and AES-OCB ciphers, potentially allowing forged messages to be accepted. This issue affects OpenSSL versions 3.0.0 to 3.0.22, 3.4.0 to 3.4.7, 3.5.0 to 3.5.8, 3.6.0 to 3.6.4, and 4.0.0 to 4.0.2. The FIPS modules in OpenSSL 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected as the impacted algorithms are not FIPS-approved. Defenders should prioritize verifying and updating OpenSSL to a non-vulnerable version, reviewing applications that utilize EVP_Cipher() with AEAD ciphers, and ensuring proper AEAD tag validation.

Defensive priority

Defenders should prioritize verifying and updating OpenSSL to a non-vulnerable version, reviewing applications that utilize EVP_Cipher() with AEAD ciphers, and ensuring proper AEAD tag validation.

Recommended defensive actions

• Verify and update OpenSSL to a version that addresses this vulnerability
• Review applications using EVP_Cipher() with AEAD ciphers and ensure proper AEAD tag validation
• Implement compensating controls to detect and prevent acceptance of forged messages
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The issue arises from EVP_Cipher() not verifying AEAD tags for empty ciphertexts with ChaCha20-Poly1305 and AES-OCB ciphers. Official OpenSSL patches are available. Affected OpenSSL versions include 3.0.0 to 3.0.22, 3.4.0 to 3.4.7, 3.5.0 to 3.5.8, 3.6.0 to 3.6.4, and 4.0.0 to 4.0.2. The FIPS modules in OpenSSL 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected as the impacted algorithms are not FIPS-approved. Defenders should verify OpenSSL versions and review applications using EVP_Cipher() with AEAD ciphers.

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.