Linux: Use After Free
CVE-2026-64523 is a critical-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 22e371a93563c30ebebc576db049785e0d7fc617, 685b10dd0e32c7782cead16c8cf055c609678583, b913801ad9b9a51437d84d030ec6843e08976bd6 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.45% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to 22e371a93563c30ebebc576db049785e0d7fc617 or 685b10dd0e32c7782cead16c8cf055c609678583 or b913801ad9b9a51437d84d030ec6843e08976bd6 or 16eaba5aa89c04eea125905bb8f988c1897f4f29, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.160 or 6.12.93 or 6.18.44 or 7.0.12, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 3b3009ea8abb713b022d94fba95ec270cf6e7eae up to, but not including, 22e371a93563c30ebebc576db049785e0d7fc617; 3b3009ea8abb713b022d94fba95ec270cf6e7eae up to, but not including, 685b10dd0e32c7782cead16c8cf055c609678583; 3b3009ea8abb713b022d94fba95ec270cf6e7eae up to, but not including, b913801ad9b9a51437d84d030ec6843e08976bd6; 3b3009ea8abb713b022d94fba95ec270cf6e7eae up to, but not including, 16eaba5aa89c04eea125905bb8f988c1897f4f29; 3b3009ea8abb713b022d94fba95ec270cf6e7eae up to, but not including, 09dba37eee70d0596e26645015f1aa95a9848e9d; 6.4 | 22e371a93563c30ebebc576db049785e0d7fc617, 685b10dd0e32c7782cead16c8cf055c609678583, b913801ad9b9a51437d84d030ec6843e08976bd6, 16eaba5aa89c04eea125905bb8f988c1897f4f29, 09dba37eee70d0596e26645015f1aa95a9848e9d |
| Linux | Linux Kernel | 6.4 up to, but not including, 6.6.160; 6.7 up to, but not including, 6.12.93; 6.13 up to, but not including, 6.18.44; 6.19 up to, but not including, 7.0.12; 7.1 | 6.6.160, 6.12.93, 6.18.44, 7.0.12 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/09dba37eee70d0596e26645015f1aa95a9848e9d
- git.kernel.org/stable/c/16eaba5aa89c04eea125905bb8f988c1897f4f29
- git.kernel.org/stable/c/22e371a93563c30ebebc576db049785e0d7fc617
- git.kernel.org/stable/c/685b10dd0e32c7782cead16c8cf055c609678583
- git.kernel.org/stable/c/b913801ad9b9a51437d84d030ec6843e08976bd6
Recent Use After Free vulnerabilities
- 7.8 High severity
- 8.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
Spotted an error? Tell us.