CVE-2026-75803 OpenSSL CVE debrief

Who should care

Developers and maintainers of applications using OpenSSL's EVP_Cipher() with AEAD ciphers, especially those handling empty ciphertexts or expecting AEAD tag validation, should review and update their applications to handle empty ciphertexts correctly. Security teams and vulnerability management teams should also be aware of the potential impact on their managed environments and plan for vendor-supported updates or mitigations as needed. Additionally, operators and platform administrators may need to assess the vulnerability's impact on their systems and prioritize remediation efforts accordingly. Monitoring and detection teams should check relevant logs for exposed assets that need extra review. Asset inventory managers should track exceptions and retest remediated assets to ensure thorough coverage. The vulnerability's impact on FIPS modules in OpenSSL versions 4.0, 3.6, 3.5, 3.4, and 3.0 is not affected as the affected algorithms are not FIPS approved and thus not implemented in the FIPS module. However, this does not negate the need for review as other components may still be vulnerable. Overall, a broad range of stakeholders across development, operations, and security teams should be aware of this vulnerability and take appropriate actions to mitigate its impact. This includes reviewing compensating controls for exposed systems while remediation is scheduled and verified, and ensuring that proper change management processes are in place for updates. The vulnerability's severity and potential impact underscore the importance of prompt attention and thorough remediation efforts across affected environments. By taking proactive steps to address this vulnerability, organizations can reduce their risk exposure and protect against potential attacks. Effective communication and coordination between teams will be crucial in ensuring a comprehensive and timely response to this vulnerability. In addition to immediate remediation efforts, organizations should also consider longer-term strategies to enhance their vulnerability management practices and improve their overall security posture. This may involve implementing additional security controls, enhancing incident

Technical summary

The EVP_Cipher() API call for AEAD ciphers like AES-OCB and ChaCha20-Poly1305 skips AEAD tag verification when an empty ciphertext is passed. This may lead to applications accepting forged messages if they rely solely on the EVP_Cipher() return value for AEAD tag validation. Affected products likely include applications using OpenSSL's EVP_Cipher() with AEAD ciphers, especially those handling empty ciphertexts or expecting AEAD tag validation.

Defensive priority

Applications using EVP_Cipher() with AEAD ciphers like AES-OCB and ChaCha20-Poly1305 should verify authentication tags for empty ciphertexts.

Recommended defensive actions

• Verify authentication tags for empty ciphertexts when using EVP_Cipher() with AEAD ciphers
• Review and update applications to handle empty ciphertexts correctly
• Monitor for potential forged messages due to improper AEAD tag validation
• 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 EVP_Cipher() API call for AEAD ciphers like AES-OCB and ChaCha20-Poly1305 skips AEAD tag verification when an empty ciphertext is passed. Callers may incorrectly assume a successful return indicates a valid AEAD tag. Source confidence is high based on OpenSSL's official advisory. However, detailed impact scope remains unclear without further product-specific analysis. Defenders should verify authentication tags for empty ciphertexts and review applications' handling of EVP_Cipher() return values.

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.