CVE-2026-23739: Asterisk is an open source private branch exchange and telephony toolkit

Q: How do I fix CVE-2026-23739?

asterisk: upgrade to 20.18.2, 21.12.1, 22.8.2, 23.2.2; certified asterisk: upgrade to newer than 18.9. Exact commands for each OS are on this page.

Q: Is CVE-2026-23739 being exploited?

CVE-2026-23739 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-23739 affect?

CVE-2026-23739 affects asterisk, certified asterisk. Severity is low (CVSS 2.0). 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

Q: How urgent is CVE-2026-23739?

Priority 10/100. No elevated risk signals yet.

Routine

LOW 2.0UPGRADEUPGRADE

CVE-2026-23739 is a low-severity flaw (CVSS 2.0) affecting asterisk, certified asterisk. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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-suppli

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	2.0 (Low)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	High
User interaction	Required
EPSS exploit chance	0.2% (top 89%)
CISA exploited list	No
Weakness	CWE-611
Published	2026-02-06
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: sangoma

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-02-06 17:16 UTCPublished CVE record published
2026-06-17 10:22 UTCUpdated Record last modified

sangoma asterisk UPGRADE

Affected: < 20.18.2 · >= 21.0.0 and < 21.12.1 · >= 22.0.0 and < 22.8.2 · >= 23.0.0 and < 23.2.2

Fixed in: 20.18.2, 21.12.1, 22.8.2, 23.2.2

Safe to downgrade to: a release before 21.0.0

1. Check installed version

apt-cache policy asterisk || rpm -q asterisk || asterisk --version

2. UPGRADE to 20.18.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade asterisk

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade asterisk

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 21.0.0 (Debian / Ubuntu)

apt-cache madison asterisk sudo apt install asterisk=<VERSION_BEFORE_21.0.0> sudo apt-mark hold asterisk

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list asterisk sudo dnf downgrade asterisk-<VERSION_BEFORE_21.0.0> sudo dnf versionlock add asterisk

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

sangoma certified asterisk UPGRADE

Affected: <= 18.9 · 20.7 cert1 · 20.7 cert1-rc1 · 20.7 cert1-rc2 · 20.7 cert2 · 20.7 cert3 · 20.7 cert4 · 20.7 cert5

Fixed in: newer than 18.9

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy certified-asterisk || rpm -q certified-asterisk || certified-asterisk --version

2. UPGRADE to newer than 18.9 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade certified-asterisk

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade certified-asterisk

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-23739?

asterisk: upgrade to 20.18.2, 21.12.1, 22.8.2, 23.2.2; certified asterisk: upgrade to newer than 18.9. Exact commands for each OS are on this page.

Is CVE-2026-23739 being exploited?

CVE-2026-23739 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-23739 affect?

CVE-2026-23739 affects asterisk, certified asterisk. Severity is low (CVSS 2.0). 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

How urgent is CVE-2026-23739?

Priority 10/100. No elevated risk signals yet.

Related CVEs

CVE-2025-1131 HIGH 7.8 UPGRADE DOWNGRADE A local privilege escalation vulnerability exists in the safe_asterisk script included with the Asterisk toolk
CVE-2026-23741 NONE 0.0 UPGRADE UPGRADE Asterisk is an open source private branch exchange and telephony toolkit
CVE-2026-23740 NONE 0.0 DOWNGRADE UPGRADE Asterisk is an open source private branch exchange and telephony toolkit
CVE-2026-23738 LOW 3.5 UPGRADE UPGRADE Asterisk is an open source private branch exchange and telephony toolkit
CVE-2025-57767 HIGH 7.5 UPGRADE Asterisk is an open source private branch exchange and telephony toolkit

References

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