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VulnerabilityPublished Updated

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

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 9.8 Critical · fixed in b913801ad9b9a51437d84d030ec6843e08976bd6 : 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
0.6% chance of exploitation in 30 days – higher than 51% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
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 b913801ad9b9a51437d84d030ec6843e08976bd6, 685b10dd0e32c7782cead16c8cf055c609678583, 22e371a93563c30ebebc576db049785e0d7fc617 +2
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 25 Jul 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
LinuxLinuxAffected
  • ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < b913801ad9b9a51437d84d030ec6843e08976bd6
Fixed in
  • b913801ad9b9a51437d84d030ec6843e08976bd6
LinuxLinuxAffected
  • ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < 685b10dd0e32c7782cead16c8cf055c609678583
Fixed in
  • 685b10dd0e32c7782cead16c8cf055c609678583
LinuxLinuxAffected
  • ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < 22e371a93563c30ebebc576db049785e0d7fc617
Fixed in
  • 22e371a93563c30ebebc576db049785e0d7fc617
LinuxLinuxAffected
  • ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < 16eaba5aa89c04eea125905bb8f988c1897f4f29
Fixed in
  • 16eaba5aa89c04eea125905bb8f988c1897f4f29
LinuxLinuxAffected
  • ≥ 3b3009ea8abb713b022d94fba95ec270cf6e7eae, < 09dba37eee70d0596e26645015f1aa95a9848e9d
Fixed in
  • 09dba37eee70d0596e26645015f1aa95a9848e9d
LinuxLinuxAffected
  • =6.4
Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: net/handshake: Take a long-lived file reference at submit handshake_nl_accept_doit() needs the file pointer backing req->hr_sk->sk_socket to survive the window between handshake_req_next() and the subsequent FD_PREPARE() and get_file(). The submit-side sock_hold() does not provide that. sk_refcnt keeps struct sock alive, but struct socket is owned by sock->file: when the consumer fputs the last file reference, sock_release() tears the socket down regardless of any sock_hold. Add an hr_file pointer to struct handshake_req and acquire an explicit reference on sock->file during handshake_req_submit(). handshake_complete() and handshake_req_cancel() release the reference on the completion-bit-winning path. The submit error path must also release the file reference, but after rhashtable insertion a concurrent handshake_req_cancel() can discover the request and race the error path. Gate the error-path cleanup -- sk_destruct restoration, fput, and request destruction -- with test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED), the same serialization handshake_complete() and handshake_req_cancel() already use. When cancel has already claimed ownership, the submit error path returns without touching the request; socket teardown handles final destruction. The accept-side dereferences are not yet retargeted; that change comes in the next patch.

References

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