CVE-2026-66141: Exim before 4.99.5 allows .forward privilege escalation because force_command for a pipe transport is mishandl

Q: How do I fix CVE-2026-66141?

exim: upgrade to 4.99.5. Exact commands for each OS are on this page.

Q: Is CVE-2026-66141 being exploited?

CVE-2026-66141 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-66141 affect?

CVE-2026-66141 affects exim. Severity is high (CVSS 7.4). Exim before 4.99.5 allows .forward privilege escalation because force_command for a pipe transport is mishandled.

Routine

HIGH 7.4UPGRADE

CVE-2026-66141 is a high-severity flaw (CVSS 7.4) affecting exim. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	7.4 (High)
Attack vector	Local
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.1% (top 97%)
CISA exploited list	No
Weakness	CWE-829
Published	2026-07-24
Last modified	2026-08-17

Publisher (CNA): MITRE · Vendor: exim

Last updated 2026-08-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-24 05:16 UTCPublished CVE record published
2026-08-17 19:06 UTCUpdated Record last modified

exim exim UPGRADE

Affected: < 4.99.5

Fixed in: 4.99.5

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy exim || rpm -q exim || exim --version

2. UPGRADE to 4.99.5 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade exim

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade exim

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-66141?

exim: upgrade to 4.99.5. Exact commands for each OS are on this page.

Is CVE-2026-66141 being exploited?

CVE-2026-66141 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-66141 affect?

CVE-2026-66141 affects exim. Severity is high (CVSS 7.4). Exim before 4.99.5 allows .forward privilege escalation because force_command for a pipe transport is mishandled.

How urgent is CVE-2026-66141?

Priority 27/100. High severity

Software pages

Exim vulnerabilities

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References

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