Exim before 4.99.5 allows .forward privilege escalation because force_command for a pipe transport is mishandled.

published 2026-07-24 3 mo ago modified 2026-08-17 2 mo ago also EUVD-2026-48479

cvss: 7.4; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.1%; EPSS 0.1% chance of exploitation in 30 days, percentile 3%
public exploits: 0; none known

Patch / fix

fixed in 1 distros 3

Exim Exim 4.99.5

debian ubuntu alpine

exim4 Debian 13 4.98.2-1+deb13u4
exim4 Debian 14 4.99.4-2

debian advisories DEBIAN-CVE-2026-66141

exim4 Ubuntu 22.04 LTS 4.95-4ubuntu2.11
exim4 Ubuntu 24.04 LTS 4.97-4ubuntu4.7
exim4 Ubuntu 26.04 LTS 4.99.1-1ubuntu1.4

ubuntu advisories UBUNTU-CVE-2026-66141

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

exim Alpine 3.24 4.98.5-r0

alpine advisories ALPINE-CVE-2026-66141

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-66141 updated 2026-08-31 cvss 7.4

exim: Exim: Local privilege escalation via .forward mishandling

Red Hat All currently supported Red Hat products
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: total
Assessed: 3 mo ago (2026-07-24)

Exploit prediction

0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.4	CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD	3.1	7.8	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

Exim Exim

Classification

Weakness

CWE-829 Inclusion of Functionality from Untrusted Control Sphere

References

openwall.com /lists/oss-security/2026/07/22/9
mailing-list, third-party-advisory

Sources

CVE List CVE-2026-66141
NVD CVE-2026-66141

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary