CVE-2026-64024: Linux kernel · tcp: fix stale per-CPU tcp_tw_isn leak enabling ISN prediction
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.4 Critical · fixed in 7.0.0-28.28~24.04.1 : patch Linux kernel as a priority.
Data as of 26 Oct 2026, 12:55 UTC
- EPSS
- 0.3% chance of exploitation in 30 days – higher than 23% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 7.0.0-28.28~24.04.1, 7.0.0-28.28, 7.0.0-1008.8 +3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:HExploitation 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@7.0.0-28.28?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws@7.0.0-1009.9?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure@7.0.0-1009.9?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde@7.0.0-1008.8?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp@7.0.0-1008.8?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke@7.0.0-1003.4?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
An official patch is available and should be applied to affected Linux kernel versions. The fix moves the tcp_tw_isn variable from a per-CPU variable back to the socket buffer control block to prevent ISN prediction. Users should update their Linux kernel to a version including this patch as soon as possible. No additional mitigations are indicated by the vendor advisory.
Description
A vulnerability in the Linux kernel's TCP implementation (CVE-2026-64024) involved a stale per-CPU tcp_tw_isn variable leak that could enable ISN (Initial Sequence Number) prediction. This occurred because the ISN value was stored in a per-CPU variable and could be left set when packets were dropped on certain code paths, leading to predictable ISNs for subsequent connections on the same CPU. The issue was fixed by moving the ISN storage back to the socket buffer control block. The vulnerability has a high CVSS score of 9.4 and affects multiple Linux kernel versions. A patch is available to address this issue.
References
- ubuntu.com/security/CVE-2026-64024 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-64024 (opens in a new tab)
- git.kernel.org/linus/1bbf0ced1d9db73ac7893c2187f3459288603e0d (opens in a new tab)
- ubuntu.com/security/notices/USN-8593-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8603-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8618-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8663-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8664-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8728-1 (opens in a new tab)