# CVE-2024-39929: Security feature bypass in n/a

> Remote attackers can bypass filename extension blocking in Exim by exploiting a parsing flaw, allowing delivery of executable attachments to user mailboxes.

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 4 Jul 2024
- **Updated:** 18 Mar 2025
- **Also known as:** CLEANSTART-2025-DU02255, CLSA-2024-1725550629, DEBIAN-CVE-2024-39929, DSA-5728-1, GHSA-7m4v-cwm7-4f2m, OESA-2024-2105, OESA-2024-2129, OESA-2026-1382, UBUNTU-CVE-2024-39929, USN-6939-1, openSUSE-SU-2024:0218-1, openSUSE-SU-2024:14196-1

## What is CVE-2024-39929?

CVE-2024-39929 is a medium-severity vulnerability in Exim Exim, published on 4 Jul 2024. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Exim through 4.97.1 misparses a multiline RFC 2231 header filename, and thus remote attackers can bypass a $mime_filename extension-blocking protection mechanism, and potentially deliver executable attachments to the mailboxes of end users.

Weakness: CWE-116 (Improper Encoding or Escaping of Output)

## Which versions are affected by CVE-2024-39929?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `exim` | SUSE:Package Hub 15 SP5 | All versions | 4.97.1-bp155.5.12.1 |
| `exim` | openSUSE:Leap 15.5 | All versions | 4.97.1-bp155.5.12.1 |
| `exim` | openSUSE:Tumbleweed | All versions | 4.98-1.1 |

Products: Exim Exim.

## How do I fix CVE-2024-39929?

Apply the vendor's patch.

## Is CVE-2024-39929 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2024-39929 exists.

Public exploit code:

- POC to test CVE-2024-39929 against EXIM mail servers (github_poc): https://github.com/michael-david-fry/CVE-2024-39929
- Detection method for Exim vulnerability CVE-2024-39929  (github_poc): https://github.com/rxerium/CVE-2024-39929

## 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-2024-39929 and fix it if it is affected.

What it is: CVE-2024-39929 is a medium-severity vulnerability in Exim Exim, published on 4 Jul 2024. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2024-39929 exists.

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-2024-39929/ (Markdown: https://insights.sbomify.com/CVE-2024-39929/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-39929
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-39929
- OSV: https://osv.dev/vulnerability/CVE-2024-39929

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-39929/
Summaries are generated and may contain mistakes; the official description above is the record.