Cyber Resilience

CVE-2026-23739

XXE in Sangoma Certified Asterisk ≤ 18.9

XXE
Published
06 February 2026
Modified
18 February 2026
Patch / advisory
View advisory
CVSS Score v3.1 2.0
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:L/A:N
EPSS Score 0.0018 7th percentile
Risk Priority 19 floored blend · peak EPSS

Summary

CVE-2026-23739 is a low-severity Improper Restriction of XML External Entity Reference (CWE-611) vulnerability in Sangoma Certified Asterisk. Its CVSS base score is 2.0 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 7th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to CM-6 (Configuration Settings) and SA-11 (Developer Testing and Evaluation) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A02:2025 Security Misconfiguration

EU & UK References

Vulnerability Data

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…

more

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.

CWE(s)
CWE-611

Related Threats

MITRE ATT&CK Enterprise Techniques

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1005 Data from Local System Collection
Adversaries may search local system sources, such as file systems, configuration files, local databases, virtual machine files, or process memory, to find files of interest and sensitive data prior to Exfiltration.
attack.mitre.org →
T1213 Data from Information Repositories Collection
Adversaries may leverage information repositories to mine valuable information.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-47779Same product: Sangoma Asterisk
CVE-2025-47780Same product: Sangoma Asterisk
CVE-2026-23738Same product: Sangoma Asterisk
CVE-2025-54995Same product: Sangoma Asterisk
CVE-2024-42491Same product: Sangoma Asterisk
CVE-2026-23741Same product: Sangoma Asterisk
CVE-2026-23740Same product: Sangoma Asterisk
CVE-2025-1131Same product: Sangoma Asterisk
CVE-2025-49832Same product: Sangoma Asterisk
CVE-2024-35190Same product: Sangoma Asterisk

Affected Assets

sangoma
asterisk
≤ 20.18.2 · 21.0.0 — 21.12.1 · 22.0.0 — 22.8.2
sangoma
certified asterisk
20.7 · ≤ 18.9

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V1.5.1
  • V15.3.2

Mitigating Controls (NIST 800-53 r5) AI

CM-6 Configuration Settings good match

Secure configuration settings can disable external entity processing in XML parsers.

SA-11 Developer Testing and Evaluation good match

Developer testing can discover XXE flaws through targeted XML parsing tests.

SI-10 Information Input Validation good match

Input validation can reject or sanitize XML containing external entity references.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-01 mostly match
prevents

Hardened XML parser configurations directly disable external entity resolution.

PR.PS-06 mostly match
prevents

Secure SDLC practices include input validation and safe XML parser configuration that prevent XXE.

ID.RA-01 partial match
prevents

Vulnerability scanning can discover XXE flaws but does not prevent their introduction in code.

PR.PS-02 partial match
prevents

Patching eliminates XXE-vulnerable parser versions but is only one aspect of software maintenance.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development catches XXE via static analysis and dynamic XML fuzzing.

A.8.8 Management of technical vulnerabilities mostly match
finds

Vulnerability management identifies and patches XML libraries with unsafe default entity settings.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates input validation and entity handling that directly prevents XXE.

A.8.26 Application security requirements partial match
prevents

Application security requirements explicitly call for disabling external entity processing in XML parsers.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles include safe parser configuration that mitigates external entity risks.

A.8.28 Secure coding partial match
prevents

Secure coding standards require disabling DTDs and external entities in XML processing.

References