# CVE-2024-42491: Null dereference in asterisk

> A malformed SIP URI causes Asterisk to crash when the res_resolver_unbound module is loaded, leading to denial of service.

- **Severity:** Medium 5.7 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 5 Sep 2024
- **Updated:** 3 Nov 2025
- **Also known as:** ALPINE-CVE-2024-42491, DEBIAN-CVE-2024-42491, GHSA-v428-g3cw-7hv9, UBUNTU-CVE-2024-42491

## What is CVE-2024-42491?

CVE-2024-42491 is a medium-severity vulnerability in asterisk, published on 5 Sep 2024. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

Asterisk is an open-source private branch exchange (PBX). Prior to versions 18.24.3, 20.9.3, and 21.4.3 of Asterisk and versions 18.9-cert12 and 20.7-cert2 of certified-asterisk, if Asterisk attempts to send a SIP request to a URI whose host portion starts with `.1` or `[.1]`, and res_resolver_unbound is loaded, Asterisk will crash with a SEGV. To receive a patch, users should upgrade to one of the following versions: 18.24.3, 20.9.3, 21.4.3, certified-18.9-cert12, certified-20.7-cert2. Two workarounds are available. Disable res_resolver_unbound by setting `noload = res_resolver_unbound.so` in modules.conf, or set `rewrite_contact = yes` on all PJSIP endpoints. NOTE: This may not be appropriate for all Asterisk configurations.

Weakness: CWE-476 (NULL Pointer Dereference), CWE-252 (Unchecked Return Value)

## Which versions are affected by CVE-2024-42491?

It affects 2 products.


Products: Sangoma Asterisk, Sangoma Certified Asterisk.

## How do I fix CVE-2024-42491?

Upgrade to a fixed version.

## Is CVE-2024-42491 being exploited?

There is no known exploitation of CVE-2024-42491 in the wild and no public exploit code.

## Other vulnerabilities in asterisk

- [CVE-2024-57520](https://insights.sbomify.com/CVE-2024-57520/): Path traversal in n/a (critical 9.8)
- [CVE-2025-47779](https://insights.sbomify.com/CVE-2025-47779/): Using malformed From header can forge identity with ";" or NULL in name portion (high 7.7)
- [CVE-2025-57767](https://insights.sbomify.com/CVE-2025-57767/): Asterisk can crash from a specifically malformed Authorization header in an incoming SIP request (high 7.5)
- [CVE-2022-37325](https://insights.sbomify.com/CVE-2022-37325/): Memory corruption in n/a (high 7.5)
- [CVE-2025-1131](https://insights.sbomify.com/CVE-2025-1131/): Asterisk Unsafe Shell Sourcing in safe_asterisk Leads to Local Privilege Escalation (high 7.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-42491 and fix it if it is affected.

What it is: CVE-2024-42491 is a medium-severity vulnerability in asterisk, published on 5 Sep 2024. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2024-42491 in the wild and no public exploit code.

Affected product: asterisk. 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-2024-42491/ (Markdown: https://insights.sbomify.com/CVE-2024-42491/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-42491
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-42491
- OSV: https://osv.dev/vulnerability/CVE-2024-42491

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-42491/
Summaries are generated and may contain mistakes; the official description above is the record.