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VulnerabilityPublished Updated

CVE-2025-68775: Linux kernel · net/handshake: duplicate handshake cancellations leak socket

Affects Linux kernelSource GCVE Database

0
Authoritative record:CVE-2025-68775· Critical 9.8

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

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
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:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 13 Jan 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
Ubuntu 25.10linuxpkg:deb/ubuntu/linux?arch=source&distro=questingOther threatsAffected
  • <6.17.0-22.22
Fixed in
  • 6.17.0-22.22
Ubuntu 25.10linux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=questingOther threatsAffected
  • <6.17.0-1012.12
Fixed in
  • 6.17.0-1012.12
Ubuntu 25.10linux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=questingOther threatsAffected
  • <6.17.0-1013.13
Fixed in
  • 6.17.0-1013.13
Ubuntu 25.10linux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=questingOther threatsAffected
  • 6.17.0-1003.3 – 6.17.0-1017.17
10 affected builds
Fixed in–
Ubuntu 25.10linux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=questingOther threatsAffected
  • <6.17.0-1012.12
Fixed in
  • 6.17.0-1012.12
Ubuntu 25.10linux-oraclepkg:deb/ubuntu/linux-oracle?arch=source&distro=questingOther threatsAffected
  • <6.17.0-1011.11
Fixed in
  • 6.17.0-1011.11

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

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