CVE-2025-68775: Linux kernel · net/handshake: duplicate handshake cancellations leak socket
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.8 Critical · fixed in 6.8.0-1052.55~22.04.1 : patch Linux kernel as a priority.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 0.5% chance of exploitation in 30 days – higher than 45% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.8.0-1052.55~22.04.1, 6.8.0-1059.65~22.04.1, 6.8.0-1058.65~22.04.1 +43
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 13 Jan 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 25.10linuxpkg:deb/ubuntu/linux?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threats | Affected
| Fixed in– |
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=questingOther threats | Affected
| Fixed in
|
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle?arch=source&distro=questingOther 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 should be applied to affected Linux kernel versions. The fix adds a test_and_set_bit for the HANDSHAKE_F_REQ_COMPLETED flag to detect and prevent duplicate handshake cancellations from causing reference count underflows. Users should update their systems using official Linux kernel updates or distribution-provided patches. After updating, a system reboot is required to apply the changes.
Description
A vulnerability in the Linux kernel handshake subsystem could cause a socket reference count underflow due to duplicate handshake cancellation requests. This occurs when a handshake request is cancelled but not fully removed from internal tracking structures, leading to improper reference handling if a second cancellation arrives. The issue has been resolved by adding a flag to detect duplicate cancellations. The vulnerability affects specific Linux kernel versions and has a high CVSS score of 9.8. A patch is available and should be applied to affected systems.
References
- ubuntu.com/security/CVE-2025-68775 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-68775 (opens in a new tab)
- git.kernel.org/linus/15564bd67e2975002f2a8e9defee33e321d3183f (opens in a new tab)
- git.kernel.org/stable/c/011ae80c49d9bfa5b4336f8bd387cd25c7593663 (opens in a new tab)
- git.kernel.org/stable/c/15564bd67e2975002f2a8e9defee33e321d3183f (opens in a new tab)
- git.kernel.org/stable/c/3c330f1dee3cd92b57e19b9d21dc8ce5970b09be (opens in a new tab)
- git.kernel.org/stable/c/e1641177e7fb48a0a5a06658d4aab51da6656659 (opens in a new tab)
- ubuntu.com/security/notices/USN-8177-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8179-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8177-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8183-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8184-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8179-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8185-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8183-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8179-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-8203-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8204-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-8185-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-8179-4 (opens in a new tab)