VulnerabilityPublished 13 Jan 2026Updated 19 Oct 2026

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

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 9.8 Critical · fixed in e1641177e7fb48a0a5a06658d4aab51da6656659 : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 13:47 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.

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers can reliably automate steps 1–4 of the kill chain
Technical impact: Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch

Available – fixed in e1641177e7fb48a0a5a06658d4aab51da6656659, 15564bd67e2975002f2a8e9defee33e321d3183f, 011ae80c49d9bfa5b4336f8bd387cd25c7593663 +1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation 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.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Linux kernel to e1641177e7fb48a0a5a06658d4aab51da6656659, 15564bd67e2975002f2a8e9defee33e321d3183f, 011ae80c49d9bfa5b4336f8bd387cd25c7593663 or 3c330f1dee3cd92b57e19b9d21dc8ce5970b09be.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < e1641177e7fb48a0a5a06658d4aab51da6656659	Fixed in e1641177e7fb48a0a5a06658d4aab51da6656659
LinuxLinux	Affected ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < 15564bd67e2975002f2a8e9defee33e321d3183f	Fixed in 15564bd67e2975002f2a8e9defee33e321d3183f
LinuxLinux	Affected ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < 011ae80c49d9bfa5b4336f8bd387cd25c7593663	Fixed in 011ae80c49d9bfa5b4336f8bd387cd25c7593663
LinuxLinux	Affected ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < 3c330f1dee3cd92b57e19b9d21dc8ce5970b09be	Fixed in 3c330f1dee3cd92b57e19b9d21dc8ce5970b09be
LinuxLinux	Affected =6.4	Fixed in–

AI-suggested

A fix is available and has been applied in the Linux kernel. Users should update to the fixed kernel versions identified by the commits e1641177e7fb48a0a5a06658d4aab51da6656659, 15564bd67e2975002f2a8e9defee33e321d3183f, 011ae80c49d9bfa5b4336f8bd387cd25c7593663f, and 3c330f1dee3cd92b57e19b9d21dc8ce5970b09be. No other mitigation is required once patched.

Description

CVE-2025-68775 is a critical vulnerability in the Linux kernel affecting version 6.4. It involves a flaw in the network handshake cancellation logic where duplicate cancellation requests can cause a socket reference count underflow, leading to resource leaks. The issue arises because a handshake request is removed from one internal list but remains in another, allowing a second cancellation to incorrectly increment socket references. This vulnerability has been fixed by adding a flag to detect duplicate cancellations.

Impact

The vulnerability allows an attacker or a network condition to cause socket reference count underflow and resource leaks in the Linux kernel. This can degrade system stability and availability by exhausting socket resources. The CVSS score of 9.8 indicates critical impact with high confidentiality, integrity, and availability consequences.

Summary

This vulnerability in the Linux kernel's network handshake code occurs when a handshake request is cancelled twice. The first cancellation removes the request from the handshake request list but leaves it in a hash table. A second cancellation for the same request causes the code to add an extra reference to the socket, resulting in a reference count underflow and a socket leak. This can happen in scenarios such as SUNRPC client-server TLS handshake timeouts. The fix involves setting a completion flag during cancellation to prevent processing duplicate cancels.

CWE-662Improper Synchronization (opens in a new tab)
Class weakness
The product utilizes multiple threads, processes, components, or systems to allow temporary access to a shared resource that can only be exclusive to one process at a time, but it does not properly synchronize these actions, which might cause simultaneous accesses of this resource by multiple threads or processes.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Implementation
Use industry standard APIs to synchronize your code.
Attack patterns
Leveraging Race Conditions via Symbolic Links (opens in a new tab)
Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions (opens in a new tab)
Forced Deadlock (opens in a new tab)
Leveraging Race Conditions (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 12:27 UTC

WeaknessesCWE-662

Technical details

References

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