# CVE-2026-66141: Privilege escalation in Exim

> Attackers can escalate privileges via mishandled force_command in pipe transports, affecting Exim mail server deployments.

- **Severity:** High 7.4 (`CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Jul 2026
- **Updated:** 24 Jul 2026
- **Also known as:** CLSA-2026-1787310808, DEBIAN-CVE-2026-66141, GHSA-mffw-2crm-m32h, ROOT-OS-DEBIAN-11-CVE-2026-66141, ROOT-OS-DEBIAN-12-CVE-2026-66141, UBUNTU-CVE-2026-66141

## What is CVE-2026-66141?

CVE-2026-66141 is a high-severity vulnerability in Exim Exim, published on 24 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

Weakness: CWE-829 (Inclusion of Functionality from Untrusted Control Sphere)

## Which versions are affected by CVE-2026-66141?

It affects 1 product.


Products: Exim Exim.

## How do I fix CVE-2026-66141?

Upgrade to a fixed version.

## Is CVE-2026-66141 being exploited?

There is no known exploitation of CVE-2026-66141 in the wild and no public exploit code.

## Other vulnerabilities in Exim Exim

- [CVE-2026-45185](https://insights.sbomify.com/CVE-2026-45185/): Use after free in Exim (critical 9.8)
- [CVE-2023-42115](https://insights.sbomify.com/CVE-2023-42115/): Exim AUTH Out-Of-Bounds Write Remote Code Execution Vulnerability (critical 9.8)
- [CVE-2020-28017](https://insights.sbomify.com/CVE-2020-28017/): Integer overflow in n/a (critical 9.8)
- [CVE-2020-28018](https://insights.sbomify.com/CVE-2020-28018/): Use after free in n/a (critical 9.8)
- [CVE-2020-28020](https://insights.sbomify.com/CVE-2020-28020/): Integer overflow in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66141 and fix it if it is affected.

What it is: CVE-2026-66141 is a high-severity vulnerability in Exim Exim, published on 24 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-66141 in the wild and no public exploit code.

Affected product: Exim Exim. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-66141/ (Markdown: https://insights.sbomify.com/CVE-2026-66141/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66141
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66141
- OSV: https://osv.dev/vulnerability/CVE-2026-66141

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-66141/
Summaries are generated and may contain mistakes; the official description above is the record.