CVE-2026-39863: Kamailio is an open source implementation of a SIP Signaling Server

This month

HIGH 7.5REMOTEUPGRADE

CVE-2026-39863 is a high-severity flaw (CVSS 7.5) 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 6.1.1, 6.0.6, and 5.8.8, an out-of-bounds access in the core of Kamailio (formerly OpenSER and SER) allows remote attackers to cause a denial of service (process crash) via a specially crafted data packet sent over TCP. The issue impacts Kamailio instances having TCP or TLS listeners. This vulnerability is fixed in 5.1.1, 6.0.6, and 5.8.8.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 60%)
CISA exploited list	No
Weakness	CWE-119
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: < 5.8.8 · >= 6.0.0 and < 6.0.6 · 6.1.0

Fixed in: 5.8.8, 6.0.6

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 5.8.8 (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-2026-39863?

kamailio: upgrade to 5.8.8, 6.0.6. Exact commands for each OS are on this page.

Is CVE-2026-39863 being exploited?

CVE-2026-39863 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-2026-39863 affect?

CVE-2026-39863 affects kamailio. Severity is high (CVSS 7.5). Kamailio is an open source implementation of a SIP Signaling Server. Prior to 6.1.1, 6.0.6, and 5.8.8, an out-of-bounds access in the core of Kamailio (formerly OpenSER and SER) allows remote attackers to cause a denial of service (process

How urgent is CVE-2026-39863?

Priority 41/100. High severity; Remotely exploitable, no login, no user action

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-2026-39864 MEDIUM 4.4 UPGRADE Kamailio is an open source implementation of a SIP Signaling Server

References

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