Linux: Out-of-bounds Write
CVE-2026-46173 is a high-severity out-of-bounds write 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 3d6fb8a7690c23e3213c4b008f64d89a44b98737, 640b4c00fb0e2920327435f6176cbefc3c546165, 7b2800ba5f5f77a8ee7f4cbadb19cf1264597a34 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 0.13% 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 3d6fb8a7690c23e3213c4b008f64d89a44b98737 or 640b4c00fb0e2920327435f6176cbefc3c546165 or 7b2800ba5f5f77a8ee7f4cbadb19cf1264597a34 or 6f49f94f3b11fe8bff1bf2a054143789e76aaf17, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.1.175 or 6.6.140 or 6.12.88 or 6.18.30, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 7f80a2fd7db9a55894fd841915236aca611291b5 up to, but not including, 3d6fb8a7690c23e3213c4b008f64d89a44b98737; 7f80a2fd7db9a55894fd841915236aca611291b5 up to, but not including, 640b4c00fb0e2920327435f6176cbefc3c546165; 7f80a2fd7db9a55894fd841915236aca611291b5 up to, but not including, 7b2800ba5f5f77a8ee7f4cbadb19cf1264597a34; 7f80a2fd7db9a55894fd841915236aca611291b5 up to, but not including, 6f49f94f3b11fe8bff1bf2a054143789e76aaf17; 7f80a2fd7db9a55894fd841915236aca611291b5 up to, but not including, 9756b3db5db6c2f5eccb32dddbd88eb4c54f575e; 7f80a2fd7db9a55894fd841915236aca611291b5 up to, but not including, c1fa0bb633e4a6b11e83ffc57fa5abe8ebb87891; 5.17 | 3d6fb8a7690c23e3213c4b008f64d89a44b98737, 640b4c00fb0e2920327435f6176cbefc3c546165, 7b2800ba5f5f77a8ee7f4cbadb19cf1264597a34, 6f49f94f3b11fe8bff1bf2a054143789e76aaf17, 9756b3db5db6c2f5eccb32dddbd88eb4c54f575e, c1fa0bb633e4a6b11e83ffc57fa5abe8ebb87891 |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) | V3.1.6 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; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 TM MFP - GNU/Linux subsystem | all versions | Not stated |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Linux | Linux Kernel | 5.17 up to, but not including, 6.1.175; 6.2 up to, but not including, 6.6.140; 6.7 up to, but not including, 6.12.88; 6.13 up to, but not including, 6.18.30; 6.19 up to, but not including, 7.0.7; 7.1 | 6.1.175, 6.6.140, 6.12.88, 6.18.30, 7.0.7 |
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: exit: prevent preemption of oopsing TASK_DEAD task When an already-exiting task oopses, make_task_dead() currently calls do_task_dead() with preemption enabled. That is forbidden: do_task_dead() calls __schedule(), which has a comment saying "WARNING: must be called with preemption disabled!". If an oopsing task is preempted in do_task_dead(), between becoming TASK_DEAD and entering the scheduler explicitly, bad things happen: finish_task_switch() assumes that once the scheduler has switched away from a TASK_DEAD task, the task can never run again and its stack is no longer needed; but that assumption apparently doesn't hold if the dead task was preempted (the SM_PREEMPT case). This means that the scheduler ends up repeatedly dropping references on the dead task's stack, which can lead to use-after-free or double-free of the entire task stack; in other words, two tasks can end up running on the same stack, resulting in various kinds of memory corruption. (This does not just affect "recursively oopsing" tasks; it is enough to oops once during task exit, for example in a file_operations::release handler)
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Write
The product writes data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
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/3d6fb8a7690c23e3213c4b008f64d89a44b98737
- git.kernel.org/stable/c/640b4c00fb0e2920327435f6176cbefc3c546165
- git.kernel.org/stable/c/6f49f94f3b11fe8bff1bf2a054143789e76aaf17
- git.kernel.org/stable/c/7b2800ba5f5f77a8ee7f4cbadb19cf1264597a34
- git.kernel.org/stable/c/9756b3db5db6c2f5eccb32dddbd88eb4c54f575e
- git.kernel.org/stable/c/c1fa0bb633e4a6b11e83ffc57fa5abe8ebb87891
Other references
Recent Out-of-bounds Write vulnerabilities
- 8.3 High severity
- 8.8 High severity
- 9.6 Critical severity
- 8.8 High severity
- 8.3 High severity
- 8.3 High severity
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