Linux: NULL Pointer Dereference
CVE-2026-43408 is a high-severity NULL pointer dereference 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 644b47f0574fd82aeb9d00317eca8d1f2a525c8c, 8be8911f590813e6f90bc6407ced1b23e50bc5da, 453df1f4535842bf17ff1885a225e153d7ee3374 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 644b47f0574fd82aeb9d00317eca8d1f2a525c8c or 8be8911f590813e6f90bc6407ced1b23e50bc5da or 453df1f4535842bf17ff1885a225e153d7ee3374 or 43323a5934b660afae687e8e4e95ac328615a5c4, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.78 or 6.17 or 6.18.19 or 6.19.9, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | db378e6f83ec705c6091c65d482d555edc2b0a72 up to, but not including, 644b47f0574fd82aeb9d00317eca8d1f2a525c8c; 15f519e9f883b316d86e2bb6b767a023aafd9d83 up to, but not including, 8be8911f590813e6f90bc6407ced1b23e50bc5da; 15f519e9f883b316d86e2bb6b767a023aafd9d83 up to, but not including, 453df1f4535842bf17ff1885a225e153d7ee3374; 15f519e9f883b316d86e2bb6b767a023aafd9d83 up to, but not including, 43323a5934b660afae687e8e4e95ac328615a5c4; dc5aad078abc416dd3d555c50f5308c16ba918a7; 2bfe45987eb346e299d9f763f9cd05f77011519f; 6.12.48 up to, but not including, 6.12.78; 6.6.160 up to, but not including, 6.7; and 2 more ranges | 644b47f0574fd82aeb9d00317eca8d1f2a525c8c, 8be8911f590813e6f90bc6407ced1b23e50bc5da, 453df1f4535842bf17ff1885a225e153d7ee3374, 43323a5934b660afae687e8e4e95ac328615a5c4, 6.12.78, 6.7 |
| Linux | Linux Kernel | 6.12.48 up to, but not including, 6.12.78; 6.16.8 up to, but not including, 6.17; 6.17.1 up to, but not including, 6.18.19; 6.19 up to, but not including, 6.19.9; 6.17; 7.0 | 6.12.78, 6.17, 6.18.19, 6.19.9 |
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: ceph: add a bunch of missing ceph_path_info initializers ceph_mdsc_build_path() must be called with a zero-initialized ceph_path_info parameter, or else the following ceph_mdsc_free_path_info() may crash. Example crash (on Linux 6.18.12): virt_to_cache: Object is not a Slab page! WARNING: CPU: 184 PID: 2871736 at mm/slub.c:6732 kmem_cache_free+0x316/0x400 [...] Call Trace: [...] ceph_open+0x13d/0x3e0 do_dentry_open+0x134/0x480 vfs_open+0x2a/0xe0 path_openat+0x9a3/0x1160 [...] cache_from_obj: Wrong slab cache. names_cache but object is from ceph_inode_info WARNING: CPU: 184 PID: 2871736 at mm/slub.c:6746 kmem_cache_free+0x2dd/0x400 [...] kernel BUG at mm/slub.c:634! Oops: invalid opcode: 0000 [#1] SMP NOPTI RIP: 0010:__slab_free+0x1a4/0x350 Some of the ceph_mdsc_build_path() callers had initializers, but others had not, even though they were all added by commit 15f519e9f883 ("ceph: fix race condition validating r_parent before applying state"). The ones without initializer are suspectible to random crashes. (I can imagine it could even be possible to exploit this bug to elevate privileges.) Unfortunately, these Ceph functions are undocumented and its semantics can only be derived from the code. I see that ceph_mdsc_build_path() initializes the structure only on success, but not on error. Calling ceph_mdsc_free_path_info() after a failed ceph_mdsc_build_path() call does not even make sense, but that's what all callers do, and for it to be safe, the structure must be zero-initialized. The least intrusive approach to fix this is therefore to add initializers everywhere.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: NULL Pointer Dereference
The product dereferences a pointer that it expects to be valid but is NULL.
How developers prevent this class of flaw
- For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
- Select a programming language that is not susceptible to these issues.
- Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
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
Recent NULL Pointer Dereference vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.8 High severity
- 7.5 High severity
- 7.8 High severity
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