CVE-2024-42491Network attack vector

Service crash via unchecked null DNS result

Published Sep 5, 2024 · Updated Nov 3, 2025

Denial of service in affected Asterisk and certified-asterisk releases allows remote authenticated users to crash the PBX via a malformed SIP URI. The res_resolver_unbound callback dereferences a null ub_result returned by libunbound for hostnames such as .1 instead of converting the malformed DNS query into an error. The module must be loaded, and exploitation requires a response to an attacker-controlled URI; unauthenticated reachability additionally requires anonymous calling.

CVSS severity5.7
Medium
EPSS probability0.59%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in affected Asterisk and certified-asterisk releases allows remote authenticated users to crash the PBX via a malformed SIP URI. The res_resolver_unbound callback dereferences a null ub_result returned by libunbound for hostnames such as .1 instead of converting the malformed DNS query into an error. The module must be loaded, and exploitation requires a response to an attacker-controlled URI; unauthenticated reachability additionally requires anonymous calling.

The record

CVE
CVE-2024-42491
Published
Sep 5, 2024
Updated
Nov 3, 2025
Vendor
Asterisk
Product
Asterisk
Classifications
CWE-252, CWE-476, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 5, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 18.24.3
  2. Affected versionversion=< 18.9-cert12
  3. Affected versionversion=>= 19.0.0, < 20.9.3
  4. Affected versionversion=>= 19.0, < 20.7-cert2
  5. Affected versionversion=>= 21.0.0, < 21.4.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Asterisk · Asteriskversion=< 18.24.3; version=< 18.9-cert12; version=>= 19.0.0, < 20.9.3; version=>= 19.0, < 20.7-cert2; version=>= 21.0.0, < 21.4.3

Published CVSS scores

5.7GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-252Unchecked Return Value
CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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