CVE-2026-94056 Exim CVE debrief

Who should care

Defenders responsible for Exim mail transfer agents, particularly those using Proxy-Protocol, should assess exposure and prioritize verification of Exim versions and configurations.

Why it matters

CVE-2026-94056 is a high-severity vulnerability in Exim before version 4.100.1, allowing attackers to read certain uninitialized data from stack memory when using Proxy-Protocol with an attacker-controlled proxy. Defenders should prioritize verifying Exim versions and configurations, especially those using Proxy-Protocol, to prevent potential information disclosure.

• Potential information disclosure
• Verification of Exim versions and configurations required
• Monitoring for potential information disclosure necessary

Technical summary

CVE-2026-94056 is a high-severity vulnerability in Exim before version 4.100.1. When using Proxy-Protocol with an attacker-controlled proxy, it allows attackers to read certain uninitialized data from stack memory. This issue is particularly concerning for organizations using Exim as their mail transfer agent, as it could potentially lead to information disclosure. Defenders should prioritize verifying Exim versions and configurations, especially those using Proxy-Protocol, to prevent potential information disclosure. The CVE record and NVD entry provide limited

Defensive priority

Defenders should prioritize verifying Exim versions and configurations, especially those using Proxy-Protocol, to prevent potential information disclosure.

Recommended defensive actions

• Verify Exim version and configuration
• Review Proxy-Protocol usage
• Monitor for potential information disclosure

Evidence notes

The CVE record and NVD entry provide limited information about the vulnerability. Further investigation is required to determine the full scope of affected systems and potential impact.

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.