Executive brief
Exim, a widely used mail transfer agent responsible for delivering email on Unix-like systems, contains a security flaw that allows local users to access restricted files. By providing specially crafted command-line arguments, an attacker can bypass security boundaries to read or modify sensitive data outside of the normal mail queue area. This can lead to a full takeover of the mail server or elevated system privileges, potentially compromising the confidentiality and integrity of all communications handled by the server.
Technical details
A directory traversal vulnerability (CWE-24) exists in Exim versions 4.88 through 4.99.4. The flaw is rooted in the mishandling of command-line arguments used to pass queue names through an Exim execution chain. A local attacker with command-line access can exploit this by supplying path traversal sequences (e.g., ../) to access files outside of the designated spool directory. Because Exim often operates with elevated privileges to manage mail delivery, this unauthorized file access can be leveraged to achieve full privilege escalation on the host system. The issue is resolved in version 4.99.5.
Affected products
- Exim Exim 4.88 through 4.99.4
Timeline
- 2026-06-22: other: Report received by maintainers
- 2026-06-23: other: Fix drafted
- 2026-07-13: other: Advance notice sent to distributions
- 2026-07-22: patched: Public release of version 4.99.5
- 2026-07-24: advisory: NVD publication date