VulnerabilityPublished 25 Jul 2026Updated 9 Aug 2026

CVE-2026-64523: Linux kernel · net/handshake: Take a long-lived file reference at submit

Source GCVE Database

Authoritative record:CVE-2026-64523· Critical 9.8

Not known to be exploited · CVSS 9.8 Critical · fixed in b913801ad9b9a51437d84d030ec6843e08976bd6 : patch Linux kernel as a priority.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

9.8Critical

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.6% chance of exploitation in 30 days – higher than 51% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in b913801ad9b9a51437d84d030ec6843e08976bd6, 685b10dd0e32c7782cead16c8cf055c609678583, 22e371a93563c30ebebc576db049785e0d7fc617 +2

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 25 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.

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.

ghsa-fc48-5g6g-x546

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < b913801ad9b9a51437d84d030ec6843e08976bd6	Fixed in b913801ad9b9a51437d84d030ec6843e08976bd6
LinuxLinux	Affected ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < 685b10dd0e32c7782cead16c8cf055c609678583	Fixed in 685b10dd0e32c7782cead16c8cf055c609678583
LinuxLinux	Affected ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < 22e371a93563c30ebebc576db049785e0d7fc617	Fixed in 22e371a93563c30ebebc576db049785e0d7fc617
LinuxLinux	Affected ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < 16eaba5aa89c04eea125905bb8f988c1897f4f29	Fixed in 16eaba5aa89c04eea125905bb8f988c1897f4f29
LinuxLinux	Affected ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < 09dba37eee70d0596e26645015f1aa95a9848e9d	Fixed in 09dba37eee70d0596e26645015f1aa95a9848e9d
LinuxLinux	Affected =6.4	Fixed in–

AI-suggested

A fix has been implemented in the Linux kernel to properly manage file references during handshake request submission, preventing premature socket teardown. Users should apply the official kernel patch that includes this fix. No additional mitigations are indicated.

Description

A critical vulnerability in the Linux kernel's net/handshake component was resolved. The issue involved improper handling of file references related to socket structures during handshake request submission, which could lead to socket teardown prematurely. The fix added explicit file reference management to ensure socket lifetime is properly maintained during request processing.

Impact

The vulnerability could cause premature teardown of socket structures during handshake request processing, potentially leading to denial of service or other critical impacts on network communication. The CVSS score of 9.8 indicates high impact on confidentiality, integrity, and availability if exploited.

Summary

CVE-2026-64523 addresses a vulnerability in the Linux kernel's net/handshake code where the handshake_nl_accept_doit() function requires a long-lived file pointer for the socket backing req->hr_sk->sk_socket. The existing sock_hold() call only maintains the struct sock, but the struct socket is owned by sock->file, which can be released prematurely causing socket teardown. The patch adds an explicit hr_file pointer to struct handshake_req and acquires a reference on sock->file during handshake_req_submit(), releasing it appropriately on completion or cancellation. The error path cleanup is gated to avoid races with concurrent cancellation. This fix ensures the socket remains valid throughout the handshake request lifecycle.

References

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