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AsteriskApplication · Sangoma

CVE-2026-23739

MEDIUM · 6.5 CVSS v3.1 Published 2026-02-06
Fix available
A fix is available. Upgrade to 20.18.2 / 21.12.1 or later.
See remediation →
72/100
Remediation priority · Elevated
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Asterisk is an open source private branch exchange and telephony toolkit. Prior to versions 20.7-cert9, 20.18.2, 21.12.1, 22.8.2, and 23.2.2, the ast_xml_open() function in xml.c parses XML documents using libxml with unsafe parsing options that enable entity expansion and XInclude processing. Specifically, it invokes xmlReadFile() with the XML_PARSE_NOENT flag and later processes XIncludes via xmlXIncludeProcess().If any untrusted or user-supplied XML file is passed to this function, it can allow an attacker to trigger XML External Entity (XXE) or XInclude-based local file disclosure, potentially exposing sensitive files from the host system. This can also be triggered in other cases in which the user is able to supply input in xml format that triggers the asterisk process to parse it. This issue has been patched in versions 20.7-cert9, 20.18.2, 21.12.1, 22.8.2, and 23.2.2.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Asterisk's ast_xml_open() function in xml.c uses unsafe libxml parsing options, specifically XML_PARSE_NOENT (which enables entity expansion) followed by xmlXIncludeProcess(), allowing XML External Entity (XXE) attacks and XInclude-based local file disclosure when processing untrusted or user-supplied XML input.

MitigationUpgrade Asterisk to version 20.7-cert9, 20.18.2, 21.12.1, 22.8.2, or 23.2.2 or later. If immediate patching is not possible, restrict or disable XML processing from untrusted sources.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
AsteriskApplication
Affected:< 20.18.2>= 21.0.0, < 21.12.1>= 22.0.0, < 22.8.2>= 23.0.0, < 23.2.2
Certified AsteriskApplication
Affected:<= 18.9= 20.7

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine Asterisk version
    Run `asterisk -V` or `asterisk -x 'core show version'` to get the installed version
    Affected if Version is < 20.18.2; or >= 21.0.0 and < 21.12.1; or >= 22.0.0 and < 22.8.2; or >= 23.0.0 and < 23.2.2; or for Certified: <= 18.9 or = 20.7
  2. Identify XML processing usage
    Search source code or check for modules that call ast_xml_open() function in xml.c. Look for where XML parsing is invoked in your Asterisk installation
    Affected if ast_xml_open() is called with XML_PARSE_NOENT enabled followed by xmlXIncludeProcess() on untrusted input
  3. Audit XML input sources
    Review configuration files in /etc/asterisk/ and any external interfaces (AMI, ARI, AGI scripts) that accept XML input from users or external systems
    Affected if Untrusted or user-supplied XML can be passed to Asterisk's XML parsing functions
  4. Check for XML-based features
    Inspect loaded modules and configurations for features that process XML such as CEL, CDR with XML formatting, or custom XML-based configs
    Affected if Features that process XML from potentially untrusted sources are enabled and accessible

You are affected if your Asterisk version falls within the affected ranges AND untrusted or user-supplied XML input can reach the ast_xml_open() function in xml.c.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 20.18.2 / 21.12.1 / 22.8.2 or later
Fixed in 20.18.221.12.122.8.2
Interim mitigation

Upgrade Asterisk to version 20.7-cert9, 20.18.2, 21.12.1, 22.8.2, or 23.2.2 or later. If immediate patching is not possible, restrict or disable XML processing from untrusted sources.

Recommended fix High confidence

Upgrade to Asterisk 20.18.2, 21.12.1, 22.8.2, or 23.2.2 (or Certified Asterisk 20.7-cert9) depending on the branch in use

  1. 1. Identify current Asterisk version by running 'asterisk -V' or checking the package manager
  2. 2. Stop the Asterisk service (e.g., 'systemctl stop asterisk' or 'service asterisk stop')
  3. 3. Backup the existing Asterisk configuration directory (/etc/asterisk by default) and any custom scripts
  4. 4. Remove the existing Asterisk packages using the package manager (e.g., 'apt remove asterisk' or 'yum remove asterisk')
  5. 5. Update the package repository to ensure access to the latest packages
  6. 6. Install the fixed version: 20.18.2 for the 20.x branch, 21.12.1 for the 21.x branch, 22.8.2 for the 22.x branch, or 23.2.2 for the 23.x branch. For Certified Asterisk users: install version 20.7-cert9
  7. 7. Start the Asterisk service (e.g., 'systemctl start asterisk' or 'service asterisk start')
  8. 8. Verify the Asterisk process is running and the version is correct: 'asterisk -V'
Caveat Review Asterisk release notes for the target version to check for configuration or feature changes that may affect existing setups

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Asterisk Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA2.0 h
9.0 hours of engineering $1,600
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-23739 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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