CVE-2026-63836: Linux kernel · batman-adv: tp_meter: avoid divide-by-zero for dec_cwnd
Affects Linux kernelSource GCVE Database
Not known to be exploited · fixed in 5.15.0-1117.124~20.04.1 : update Linux kernel when convenient.
Data as of 26 Oct 2026, 12:55 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
- 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.
- Patch
- Available – fixed in 5.15.0-1117.124~20.04.1, 5.15.0-1123.132~20.04.1, 5.15.0-1122.131~20.04.1 +42
Exploitation evidence
Disclosed: evidence found.
CVE published 19 Jul 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
Upgrade to a fixed release listed under Affected software.
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 patch is available and has been incorporated into Linux kernel updates distributed by Ubuntu and other vendors. Users should apply the latest kernel updates as provided by their distribution to remediate this vulnerability. After updating, a system reboot is required. The vendor advisory confirms the availability of an official fix. No additional mitigation steps are necessary beyond applying the patch.
Description
A divide-by-zero vulnerability was identified and resolved in the Linux kernel's batman-adv module, specifically in the tp_meter component's dec_cwnd calculation. The issue arises from an arithmetic overflow in 32-bit unsigned calculations leading to an invalid division by zero. This flaw could cause incorrect behavior in congestion window calculations. The vulnerability affects multiple Linux kernel versions used in Azure and Ubuntu environments. A patch is available and included in recent kernel updates.
References
- nvd.nist.gov/vuln/detail/CVE-2026-63836 (opens in a new tab)
- git.kernel.org/stable/c/1381b021bf886b793fa5ffb895a8efae7ba0318f (opens in a new tab)
- git.kernel.org/stable/c/33ccd52f3cc9ed46ce395199f89aa3234dc83314 (opens in a new tab)
- git.kernel.org/stable/c/35264c4d46067d6312871488c810cef387f8c1f6 (opens in a new tab)
- git.kernel.org/stable/c/585616dab0aa9c45bc11b2c8082ca78533bc00e9 (opens in a new tab)
- git.kernel.org/stable/c/7d2a44bc6bbe39aed03c68864aa0e54e04a50278 (opens in a new tab)
- git.kernel.org/stable/c/ac229c86e49fdb96d91f51bc2fa37a9c4f58c44f (opens in a new tab)
- git.kernel.org/stable/c/cd74176cf1685f35a2e5f212d15748bbfecb53b6 (opens in a new tab)
- git.kernel.org/stable/c/d08b69da40a101df1e28bfe1e8fa7a09ffa41107 (opens in a new tab)
- ubuntu.com/security/CVE-2026-63836 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-63836 (opens in a new tab)
- git.kernel.org/linus/33ccd52f3cc9ed46ce395199f89aa3234dc83314 (opens in a new tab)
- msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-63836.json (opens in a new tab)
- support.microsoft.com/lifecycle (opens in a new tab)
- first.org/cvss (opens in a new tab)
- ubuntu.com/security/notices/USN-8726-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8727-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8760-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8726-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8726-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8800-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8760-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8726-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8878-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8879-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8877-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8875-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8875-2 (opens in a new tab)