Linux: Use After Free
CVE-2026-23458 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 d8cd0efbccc5cfb0a80da744a7da76e1333ab925, 9821b47f669eb82791fa0b1a6ebaf9aa219bea72, bdf2724eefd4455a66863abb025bab8d3aa98c57 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 0.14% 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 d8cd0efbccc5cfb0a80da744a7da76e1333ab925 or 9821b47f669eb82791fa0b1a6ebaf9aa219bea72 or bdf2724eefd4455a66863abb025bab8d3aa98c57 or f04cc86d59906513d2d62183b882966fc0ae0390, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.253 or 5.15.203 or 6.1.167 or 6.6.130, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | e844a928431fa8f1359d1f4f2cef53d9b446bf52 up to, but not including, d8cd0efbccc5cfb0a80da744a7da76e1333ab925; e844a928431fa8f1359d1f4f2cef53d9b446bf52 up to, but not including, 9821b47f669eb82791fa0b1a6ebaf9aa219bea72; e844a928431fa8f1359d1f4f2cef53d9b446bf52 up to, but not including, bdf2724eefd4455a66863abb025bab8d3aa98c57; e844a928431fa8f1359d1f4f2cef53d9b446bf52 up to, but not including, f04cc86d59906513d2d62183b882966fc0ae0390; e844a928431fa8f1359d1f4f2cef53d9b446bf52 up to, but not including, f025171feef2ac65663d7986f1d5ff0c28d6b2a9; e844a928431fa8f1359d1f4f2cef53d9b446bf52 up to, but not including, 04c8907ce4e3d3e26c5e1a3e47aa5d17082cbb56; e844a928431fa8f1359d1f4f2cef53d9b446bf52 up to, but not including, cd541f15b60e2257441398cf495d978f816d09f8; e844a928431fa8f1359d1f4f2cef53d9b446bf52 up to, but not including, 5cb81eeda909dbb2def209dd10636b51549a3f8a; and 1 more ranges | d8cd0efbccc5cfb0a80da744a7da76e1333ab925, 9821b47f669eb82791fa0b1a6ebaf9aa219bea72, bdf2724eefd4455a66863abb025bab8d3aa98c57, f04cc86d59906513d2d62183b882966fc0ae0390, f025171feef2ac65663d7986f1d5ff0c28d6b2a9, 04c8907ce4e3d3e26c5e1a3e47aa5d17082cbb56 |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) | V3.1.6 and later; V3.1.5 and later; V3.1.7 and later | Not stated |
| Linux | Linux Kernel | 3.10 up to, but not including, 5.10.253; 5.11 up to, but not including, 5.15.203; 5.16 up to, but not including, 6.1.167; 6.2 up to, but not including, 6.6.130; 6.7 up to, but not including, 6.12.78; 6.13 up to, but not including, 6.18.20; 6.19 up to, but not including, 6.19.10; 7.0 | 5.10.253, 5.15.203, 6.1.167, 6.6.130, 6.12.78, 6.18.20 |
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: netfilter: ctnetlink: fix use-after-free in ctnetlink_dump_exp_ct() ctnetlink_dump_exp_ct() stores a conntrack pointer in cb->data for the netlink dump callback ctnetlink_exp_ct_dump_table(), but drops the conntrack reference immediately after netlink_dump_start(). When the dump spans multiple rounds, the second recvmsg() triggers the dump callback which dereferences the now-freed conntrack via nfct_help(ct), leading to a use-after-free on ct->ext. The bug is that the netlink_dump_control has no .start or .done callbacks to manage the conntrack reference across dump rounds. Other dump functions in the same file (e.g. ctnetlink_get_conntrack) properly use .start/.done callbacks for this purpose. Fix this by adding .start and .done callbacks that hold and release the conntrack reference for the duration of the dump, and move the nfct_help() call after the cb->args[0] early-return check in the dump callback to avoid dereferencing ct->ext unnecessarily. BUG: KASAN: slab-use-after-free in ctnetlink_exp_ct_dump_table+0x4f/0x2e0 Read of size 8 at addr ffff88810597ebf0 by task ctnetlink_poc/133 CPU: 1 UID: 0 PID: 133 Comm: ctnetlink_poc Not tainted 7.0.0-rc2+ #3 PREEMPTLAZY Call Trace: <TASK> ctnetlink_exp_ct_dump_table+0x4f/0x2e0 netlink_dump+0x333/0x880 netlink_recvmsg+0x3e2/0x4b0 ? aa_sk_perm+0x184/0x450 sock_recvmsg+0xde/0xf0 Allocated by task 133: kmem_cache_alloc_noprof+0x134/0x440 __nf_conntrack_alloc+0xa8/0x2b0 ctnetlink_create_conntrack+0xa1/0x900 ctnetlink_new_conntrack+0x3cf/0x7d0 nfnetlink_rcv_msg+0x48e/0x510 netlink_rcv_skb+0xc9/0x1f0 nfnetlink_rcv+0xdb/0x220 netlink_unicast+0x3ec/0x590 netlink_sendmsg+0x397/0x690 __sys_sendmsg+0xf4/0x180 Freed by task 0: slab_free_after_rcu_debug+0xad/0x1e0 rcu_core+0x5c3/0x9c0
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
Patches and release notes
- git.kernel.org/stable/c/04c8907ce4e3d3e26c5e1a3e47aa5d17082cbb56
- git.kernel.org/stable/c/5cb81eeda909dbb2def209dd10636b51549a3f8a
- git.kernel.org/stable/c/9821b47f669eb82791fa0b1a6ebaf9aa219bea72
- git.kernel.org/stable/c/bdf2724eefd4455a66863abb025bab8d3aa98c57
- git.kernel.org/stable/c/cd541f15b60e2257441398cf495d978f816d09f8
- git.kernel.org/stable/c/d8cd0efbccc5cfb0a80da744a7da76e1333ab925
- git.kernel.org/stable/c/f025171feef2ac65663d7986f1d5ff0c28d6b2a9
- git.kernel.org/stable/c/f04cc86d59906513d2d62183b882966fc0ae0390
Other references
Recent Use After Free vulnerabilities
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