Linux: Use After Free
CVE-2026-53256 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 8.0 out of 10. It can be exploited from the same local network by an attacker with a low-privileged account, without any action from a user. The record lists versions f5ec76bdbeb80f75ad0be204371afffee0f8fac8, a07d741c077d4e34b16458241a94d29039386553, 1f73f92f66251065a5f39b09a47cf05ea14d3107 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 0.26% 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 f5ec76bdbeb80f75ad0be204371afffee0f8fac8 or a07d741c077d4e34b16458241a94d29039386553 or 1f73f92f66251065a5f39b09a47cf05ea14d3107 or de31973ef00e5aa55496f84cf6a44bb157a34e02, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.259 or 5.15.210 or 6.1.176 or 6.6.143, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, f5ec76bdbeb80f75ad0be204371afffee0f8fac8; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, a07d741c077d4e34b16458241a94d29039386553; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 1f73f92f66251065a5f39b09a47cf05ea14d3107; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, de31973ef00e5aa55496f84cf6a44bb157a34e02; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, b0e33e409715c617e2a20f46f99aa5403a14dfda; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 8802413ce63175fb522a2bd609fb043a3550c720; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 6f4462d12133106460d7c046b95aad2491e3fddf; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 43c441edacf953b39517a44f5e5e10a93618b226; and 1 more ranges | f5ec76bdbeb80f75ad0be204371afffee0f8fac8, a07d741c077d4e34b16458241a94d29039386553, 1f73f92f66251065a5f39b09a47cf05ea14d3107, de31973ef00e5aa55496f84cf6a44bb157a34e02, b0e33e409715c617e2a20f46f99aa5403a14dfda, 8802413ce63175fb522a2bd609fb043a3550c720 |
| Siemens | SIMATIC S7-1500 TM MFP - GNU/Linux subsystem | all versions | Not stated |
| Linux | Linux Kernel | 2.6.12.1 up to, but not including, 5.10.259; 5.11 up to, but not including, 5.15.210; 5.16 up to, but not including, 6.1.176; 6.2 up to, but not including, 6.6.143; 6.7 up to, but not including, 6.12.94; 6.13 up to, but not including, 6.18.36; 6.19 up to, but not including, 7.0.13; 2.6.12; and 1 more ranges | 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36 |
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
- AdjacentThe attacker must be on the same local network segment.
- 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:A/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: Bluetooth: RFCOMM: hold listener socket in rfcomm_connect_ind() rfcomm_get_sock_by_channel() scans rfcomm_sk_list under the list lock, but returns the selected listener after dropping that lock without taking a reference. rfcomm_connect_ind() then locks the listener, queues a child socket on it, and may notify it after unlocking it. The buggy scenario involves two paths, with each column showing the order within that path: rfcomm_connect_ind(): listener close: 1. Find parent in 1. close() enters rfcomm_get_sock_by_channel() rfcomm_sock_release(). 2. Drop rfcomm_sk_list.lock 2. rfcomm_sock_shutdown() without pinning parent. closes the listener. 3. Call lock_sock(parent) and 3. rfcomm_sock_kill() bt_accept_enqueue(parent, unlinks and puts parent. sk, true). 4. Read parent flags and may 4. parent can be freed. call sk_state_change(). If close wins the race, parent can be freed before rfcomm_connect_ind() reaches lock_sock(), bt_accept_enqueue(), or the deferred-setup callback. Take a reference on the listener before leaving rfcomm_sk_list.lock. After lock_sock() succeeds, recheck that it is still in BT_LISTEN before queueing a child, cache the deferred-setup bit while the parent is locked, and drop the reference after the last parent use. KASAN reported a slab-use-after-free in lock_sock_nested() from rfcomm_connect_ind(), with the freeing stack going through rfcomm_sock_kill() and rfcomm_sock_release().
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/1f73f92f66251065a5f39b09a47cf05ea14d3107
- git.kernel.org/stable/c/43c441edacf953b39517a44f5e5e10a93618b226
- git.kernel.org/stable/c/6f4462d12133106460d7c046b95aad2491e3fddf
- git.kernel.org/stable/c/8802413ce63175fb522a2bd609fb043a3550c720
- git.kernel.org/stable/c/a07d741c077d4e34b16458241a94d29039386553
- git.kernel.org/stable/c/b0e33e409715c617e2a20f46f99aa5403a14dfda
- git.kernel.org/stable/c/de31973ef00e5aa55496f84cf6a44bb157a34e02
- git.kernel.org/stable/c/f5ec76bdbeb80f75ad0be204371afffee0f8fac8
Other references
Recent Use After Free vulnerabilities
- 7.5 High severity
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 7.5 High severity
- 8.2 High severity
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