CVE-2025-39702: Linux kernel · ipv6: sr: Fix MAC comparison to be constant-time
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.8 Critical · fixed in 5.15.0-1097.104~20.04.1 : patch Linux kernel as a priority.
Data as of 28 Oct 2026, 11:27 UTC
- Patch
- Available – fixed in 5.15.0-1097.104~20.04.1, 5.15.0-1102.111~20.04.1, 5.15.0-1097.106~20.04.1 +58
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 5 Sep 2025
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.
Patches and advisories
- ubuntu.com/security/notices/USN-7909-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7910-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7910-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7933-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-5 (opens in a new tab)
- ubuntu.com/security/notices/USN-7938-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8031-1 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-aws-6.14pkg:deb/ubuntu/linux-aws-6.14?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=nobleOther 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 released in multiple updated Linux kernel versions, including those for Ubuntu 20.04 LTS and 22.04 LTS. Users and administrators should upgrade to the fixed kernel versions listed in the advisory to mitigate this vulnerability. No additional mitigation steps are required beyond applying the official updates.
Description
A critical vulnerability in the Linux kernel's IPv6 Segment Routing (sr) implementation was fixed by changing the MAC address comparison to a constant-time operation to prevent timing attacks. This flaw could allow attackers to exploit timing differences during MAC comparisons. Multiple Linux kernel versions, including various Azure-specific builds, are affected. The issue has been addressed in updated kernel versions released by Ubuntu and other distributions.
References
- ubuntu.com/security/CVE-2025-39702 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-39702 (opens in a new tab)
- git.kernel.org/linus/a458b2902115b26a25d67393b12ddd57d1216aaa (opens in a new tab)
- git.kernel.org/stable/c/3b348c9c8d2ca2c67559ffd0e258ae7e1107d4f0 (opens in a new tab)
- git.kernel.org/stable/c/3ddd55cf19ed6cc62def5e3af10c2a9df1b861c3 (opens in a new tab)
- git.kernel.org/stable/c/86b6d34717fe0570afce07ee79b8eeb40341f831 (opens in a new tab)
- git.kernel.org/stable/c/a458b2902115b26a25d67393b12ddd57d1216aaa (opens in a new tab)
- git.kernel.org/stable/c/b3967c493799e63f648e9c7b6cb063aa2aed04e7 (opens in a new tab)
- git.kernel.org/stable/c/f7878d47560d61e3f370aca3cebb8f42a55b990a (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7910-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7910-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7933-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7909-5 (opens in a new tab)
- ubuntu.com/security/notices/USN-7938-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8028-2 (opens in a new tab)