Linux: Use After Free
CVE-2026-64575 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions c842882e4c5d2818b858d6baf3fd10958c93f729, 7a6a6d2a127866935f87b55b557bc89693065462, f0c1810320b0dac228103fad7311e89532134d83 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 0.16% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to c842882e4c5d2818b858d6baf3fd10958c93f729 or 7a6a6d2a127866935f87b55b557bc89693065462 or f0c1810320b0dac228103fad7311e89532134d83 or 9f27c4f0ae35b5390ce4f7a54d3501144e41a54d, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 9794ac757a650dd594391192183c9caf939f8223 up to, but not including, c842882e4c5d2818b858d6baf3fd10958c93f729; 1d7a82c1df5fc397eaca9c6b8c8f61aae9866ad4 up to, but not including, 7a6a6d2a127866935f87b55b557bc89693065462; 36f955807ee4ede07e9410772f792e4cb4ec807b up to, but not including, f0c1810320b0dac228103fad7311e89532134d83; cdec67a489d4fdae3e83e04fca0419136a83c4c2 up to, but not including, 9f27c4f0ae35b5390ce4f7a54d3501144e41a54d; cdec67a489d4fdae3e83e04fca0419136a83c4c2 up to, but not including, 8a726e9585ffe7bfbfad2b5279277a00973970f3; cdec67a489d4fdae3e83e04fca0419136a83c4c2 up to, but not including, 980a813452754f8001704744e92f7aa697c53dd3; 6.17 | c842882e4c5d2818b858d6baf3fd10958c93f729, 7a6a6d2a127866935f87b55b557bc89693065462, f0c1810320b0dac228103fad7311e89532134d83, 9f27c4f0ae35b5390ce4f7a54d3501144e41a54d, 8a726e9585ffe7bfbfad2b5279277a00973970f3, 980a813452754f8001704744e92f7aa697c53dd3 |
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
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- 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:L/AC:L/PR:L/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: bpf: tcp: fix double sock release on batch realloc bpf_iter_tcp_batch() releases the current batch via bpf_iter_tcp_put_batch(), which drops the socket refs and rewrites each slot with the socket cookie, then grows the batch. cur_sk/end_sk are kept for bpf_iter_tcp_resume(), but on realloc failure the function returns ERR_PTR() before resume runs, leaving cur_sk < end_sk over slots that now hold cookies rather than sock pointers. bpf_iter_tcp_seq_stop() then calls bpf_iter_tcp_put_batch() again and dereferences a cookie as a struct sock. Empty the batch on the failure path so stop() does not release it again. The sockets were already freed by the first bpf_iter_tcp_put_batch(), so nothing leaks, and a later read() rescans the bucket from the start instead of skipping it. The sibling GFP_NOWAIT failure path still holds real socket references and is left for stop() to release. BUG: KASAN: null-ptr-deref in __sock_gen_cookie Read of size 8 at addr 0000000000000059 by task exploit ... __sock_gen_cookie (net/core/sock_diag.c:28) bpf_iter_tcp_put_batch (net/ipv4/tcp_ipv4.c:2918) bpf_iter_tcp_seq_stop (net/ipv4/tcp_ipv4.c:3270) bpf_seq_read (kernel/bpf/bpf_iter.c:205) vfs_read (fs/read_write.c:572) ksys_read (fs/read_write.c:716) do_syscall_64 entry_SYSCALL_64_after_hwframe Kernel panic - not syncing: Fatal exception
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: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
- git.kernel.org/stable/c/7a6a6d2a127866935f87b55b557bc89693065462
- git.kernel.org/stable/c/8a726e9585ffe7bfbfad2b5279277a00973970f3
- git.kernel.org/stable/c/980a813452754f8001704744e92f7aa697c53dd3
- git.kernel.org/stable/c/9f27c4f0ae35b5390ce4f7a54d3501144e41a54d
- git.kernel.org/stable/c/c842882e4c5d2818b858d6baf3fd10958c93f729
- git.kernel.org/stable/c/f0c1810320b0dac228103fad7311e89532134d83
Recent Use After Free vulnerabilities
- 7.3 High severity
- 7.8 High severity
- 7.8 High severity
- 9.8 Critical severity
- 7.5 High severity
- 9.8 Critical severity
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