CVE-2026-39864: Kamailio is an open source implementation of a SIP Signaling Server

Routine

MEDIUM 4.4UPGRADE

CVE-2026-39864 is a medium-severity flaw (CVSS 4.4) affecting kamailio. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Kamailio is an open source implementation of a SIP Signaling Server. Prior to 6.0.5 and 5.8.7, an out-of-bounds read in the auth module of Kamailio (formerly OpenSER and SER) allows remote attackers to cause a denial of service (process crash) via a specially crafted SIP packet if a successful user authentication without a database backend is followed by additional user identity checks. This vulnerability is fixed in 6.0.5 and 5.8.7.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	4.4 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	High
User interaction	None
EPSS exploit chance	0.3% (top 77%)
CISA exploited list	No
Weakness	CWE-125
Published	2026-04-08
Last modified	2026-07-24

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

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-08 20:16 UTCPublished CVE record published
2026-07-24 21:10 UTCUpdated Record last modified

kamailio kamailio UPGRADE

Affected: < 5.8.7 · >= 6.0.0 and < 6.0.5

Fixed in: 5.8.7, 6.0.5

Safe to downgrade to: a release before 6.0.0

1. Check installed version

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

2. UPGRADE to 5.8.7 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade kamailio

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 6.0.0 (Debian / Ubuntu)

apt-cache madison kamailio sudo apt install kamailio=<VERSION_BEFORE_6.0.0> sudo apt-mark hold kamailio

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

dnf --showduplicates list kamailio sudo dnf downgrade kamailio-<VERSION_BEFORE_6.0.0> sudo dnf versionlock add kamailio

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.

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-2026-39864?

kamailio: upgrade to 5.8.7, 6.0.5. Exact commands for each OS are on this page.

Is CVE-2026-39864 being exploited?

CVE-2026-39864 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-2026-39864 affect?

CVE-2026-39864 affects kamailio. Severity is medium (CVSS 4.4). Kamailio is an open source implementation of a SIP Signaling Server. Prior to 6.0.5 and 5.8.7, an out-of-bounds read in the auth module of Kamailio (formerly OpenSER and SER) allows remote attackers to cause a denial of service (process cra

How urgent is CVE-2026-39864?

Priority 21/100. No elevated risk signals yet.

Related CVEs

CVE-2026-52023 HIGH 7.5 UPGRADE An issue in kamailio v.6.1.1 and before allows a remote attacker to cause a denial of service via the ims_regi
CVE-2026-52022 HIGH 7.5 UPGRADE An issue in kamailio v.6.1.1 and before allows a remote attacker to cause a denial of service via the IMS P-CS
CVE-2026-39863 HIGH 7.5 UPGRADE Kamailio is an open source implementation of a SIP Signaling Server

References

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