Exim: Path Traversal: '../filedir'
CVE-2026-66140 is a high-severity path traversal: '../filedir' vulnerability in Exim, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists version 4.99.5 as the first without the flaw, so updating Exim to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.39% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Exim to 4.99.5 or a later version.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.4 | High | CNA (mitre.org) |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
Exim before 4.99.5 allows directory traversal to access files outside of the spool area, and consequently gain privileges, because arguments related to queue-name are mishandled.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Path Traversal: '../filedir'
The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize../ sequences that can resolve to a location that is outside of that directory.
How developers prevent this class of flaw
- Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- openwall.com/lists/oss-security/2026/07/22/9Mailing List, Third Party Advisory
Other vulnerabilities in Exim
- 7.5 High severity
- 9.8 Critical severity
- 9.1 Critical severity
- 9.8 Critical severity
- 7.5 High severity
- 9.8 Critical severity
Recent Path Traversal: '../filedir' vulnerabilities
- 7.7 High severity
- 9.4 Critical severity
- 7.3 High severity
- 8.5 High severity
- 9.8 Critical severity
- 7.5 High severity
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