CVE-2026-66141 Exim vulnerability
Exim before 4.99.5 allows .forward privilege escalation because force_command for a pipe transport is mishandled.
Browse Supply Chain security risksQuick answer
Exim should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- < 4.99.5
Fixed versions
- Apply the latest vendor-supported patched version.
How to fix it
CVE-2026-66141 affects Exim and involves file access or path traversal. Successful exploitation may read, overwrite, or delete files outside the intended directory. Prioritize internet-facing, privileged, automation, and production deployments. Upgrade Exim to 4.99.5 or a later vendor-supported fixed release.
- Inventory every deployment, device, package, plugin, container, build, and environment that uses Exim.
- Compare the installed version with the recorded affected range: < 4.99.5.
- Upgrade Exim to 4.99.5 or a later vendor-supported fixed release.
- Until patched, reject absolute and parent-relative paths, confine filesystem access to an explicit root, and accept files or manifests only from trusted sources.
- Review configuration, roles, tokens, network paths, and exposed endpoints connected to Exim; remove access that is not required.
- Review filesystem, application, and audit logs for parent-directory segments, absolute paths, unexpected reads, writes, or deletions outside the intended root.
- If exploitation is suspected, isolate affected assets, preserve evidence, rotate exposed credentials or keys, restore trusted data, and rebuild compromised systems before returning them to service.
Scan now. Google sign-in is only needed to unlock fix guidance.
Verify the fix
- Confirm every affected asset now runs the fixed vendor-supported release or has the documented mitigation for CVE-2026-66141 in place.
- Use a safe regression test to confirm the affected file access or path traversal path no longer produces the vulnerable behavior.
- Confirm temporary access controls, endpoint restrictions, network blocks, and least-privilege settings remain effective after the update.
- Review post-remediation logs and rerun Fixnx plus the relevant package, dependency, firmware, browser, or product-specific security check.
- Document affected assets, versions, changes, validation evidence, reviewed logs, and any credential rotation, cleanup, or replacement completed.
Related categories
Related security risks
More published guidance from the same primary category.
Trusted references
FAQ
What is affected by CVE-2026-66141?
Exim versions listed as affected should be reviewed: < 4.99.5.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.