CVE-2026-80839: Linux kernel · batman-adv: reject unrepresentable multicast TVLV offsets
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 26 Oct 2026, 13:47 UTC
Rated by Threat Radar · CVSS not yet scored by NVD
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Exploitation evidence
Disclosed: evidence found.
CVE published 4 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.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther threats | Affected
| 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 that adds careful validation of multicast TVLV offsets before setting network and transport headers. Systems should update to the Linux kernel version that includes this patch. Since no explicit patch version is provided, users should monitor official Linux kernel advisories for the fixed version and apply updates accordingly. No additional mitigation steps are indicated.
Description
In the Linux kernel, the following vulnerability has been resolved: batman-adv: reject unrepresentable multicast TVLV offsets The network and transport header fields in struct sk_buff are 16-bit offsets from skb->head, and U16_MAX is reserved as the unset transport header value. batadv_tvlv_call_handler() sets both fields from a received multicast TVLV without checking whether the TVLV end is representable. If the end offset exceeds the field's range, skb_set_transport_header() truncates it so that the transport header precedes the network header. The negative difference is then returned by skb_network_header_len() as a large u32. batadv_mcast_forw_packet() consequently accepts an oversized multicast tracker and accesses memory beyond the skb data. Add skb_set_transport_header_careful(), an offset-aware counterpart to skb_reset_transport_header_careful(), which validates the final head-relative offset before assigning it. Use the new helper in batadv_tvlv_call_handler() and reject unrepresentable TVLVs before setting the network header.
References
- nvd.nist.gov/vuln/detail/CVE-2026-80839 (opens in a new tab)
- git.kernel.org/stable/c/1b466746fe109127fd983100a228cdd1f1f6ece2 (opens in a new tab)
- git.kernel.org/stable/c/2b46baa591d0a7c16b62f150917187e70d053be6 (opens in a new tab)
- git.kernel.org/stable/c/916ec741e65af072b98e475feaad98c063da1b7c (opens in a new tab)
- git.kernel.org/stable/c/da1f5aa7ec93f2cc17f5cd30efc54f62af433cf2 (opens in a new tab)
- git.kernel.org/stable/c/f12c2de4f542e3220e17e0606f492110064f04cb (opens in a new tab)
- ubuntu.com/security/CVE-2026-80839 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-80839 (opens in a new tab)
- git.kernel.org/linus/f12c2de4f542e3220e17e0606f492110064f04cb (opens in a new tab)