VulnerabilityPublished 16 Sep 2026Updated 5 Oct 2026

CVE-2026-89950: Linux kernel · batman-adv: mcast: linearize skbuff for packet generation

Affects Linux kernelSource GCVE Database

Not known to be exploited.

Data as of 26 Oct 2026, 12:55 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.2% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation evidence

Disclosed: evidence found.
CVE published 16 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Ubuntu 26.04 LTSlinux`pkg:deb/ubuntu/linux?arch=source&distro=resolute`Other threats	Affected 6.17.0-5.5 – 7.0.0-38.38 23 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=resolute`Other threats	Affected 6.17.0-1003.3 – 7.0.0-1017.17 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resolute`Other threats	Affected 7.0.0-1003.3 – 7.0.0-1016.16 9 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 13 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gke`pkg:deb/ubuntu/linux-gke?arch=source&distro=resolute`Other threats	Affected 7.0.0-1002.3 – 7.0.0-1008.9 6 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix has been implemented in the Linux kernel to ensure proper linearization of skbuffs during multicast packet forwarding. Users should apply the updated kernel versions that include this fix. Since the vulnerability is resolved in newer versions, upgrading to patched kernel releases is the recommended mitigation. Patch status is not explicitly stated in the input data, so users should consult the vendor advisory for the latest remediation guidance.

Description

A vulnerability in the Linux kernel's batman-adv multicast forwarding code can cause a fatal kernel BUG due to improper linearization of socket buffers (skbuff) during packet generation. This occurs because certain functions unshare but do not linearize skbuffs, triggering a SKB_LINEAR_ASSERT failure. The issue affects specific Linux kernel versions used in various Ubuntu releases.

Impact

This vulnerability can cause a kernel panic (fatal BUG) when the affected multicast forwarding code path is exercised, potentially leading to denial of service on systems running the vulnerable Linux kernel versions. There is no indication of code execution or privilege escalation from the provided data.

Summary

The Linux kernel's batman-adv multicast forwarding implementation has a flaw where the functions batadv_mcast_forw_packet() and batadv_mcast_forw_scrape() are called indirectly by multiple handlers. When invoked via batadv_mcast_forw_mcsend(), the skbuff is unshared but not linearized, violating SKB_LINEAR_ASSERT and causing a fatal BUG(). Proper linearization should occur during the expansion of the skbuff head, but this is not consistently done, leading to the vulnerability. The affected code paths include batadv_interface_tx, batadv_mcast_forw_mode, batadv_mcast_forw_mode_by_count(), and others that call batadv_mcast_forw_expand_head() before further processing.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 24 Oct 2026, 20:29 UTC

Technical details

References

Community reviews

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