Linux: Use After Free
CVE-2026-31597 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 36539c4d536f851a3b346a6ebb27b51bc3d77a94, 35c2c05261d6f6d84aaa1355afa201d507943e76, 3f5e74b5db9353b01ed50f4de84e75b755f8fbc2 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 36539c4d536f851a3b346a6ebb27b51bc3d77a94 or 35c2c05261d6f6d84aaa1355afa201d507943e76 or 3f5e74b5db9353b01ed50f4de84e75b755f8fbc2 or 6f072daefcab1d84ce37c073645615f63be91006, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.136 or 6.12.83 or 6.18.24 or 6.19.14, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 614a9e849ca6ea24843795251cb30af525d5336b up to, but not including, 36539c4d536f851a3b346a6ebb27b51bc3d77a94; 614a9e849ca6ea24843795251cb30af525d5336b up to, but not including, 35c2c05261d6f6d84aaa1355afa201d507943e76; 614a9e849ca6ea24843795251cb30af525d5336b up to, but not including, 3f5e74b5db9353b01ed50f4de84e75b755f8fbc2; 614a9e849ca6ea24843795251cb30af525d5336b up to, but not including, 6f072daefcab1d84ce37c073645615f63be91006; 614a9e849ca6ea24843795251cb30af525d5336b up to, but not including, 4cf2768a0291a0cdd0dae801ea0eafa3878a349d; 614a9e849ca6ea24843795251cb30af525d5336b up to, but not including, d45ff441b416d4aa1af72b1db23d959601c04da2; 614a9e849ca6ea24843795251cb30af525d5336b up to, but not including, 76a602fdbb78dd05b2da06f74a988cebc97e82d0; 614a9e849ca6ea24843795251cb30af525d5336b up to, but not including, 925bf22c1b823e231b1baea761fe8a1512e442f2; and 2 more ranges | 36539c4d536f851a3b346a6ebb27b51bc3d77a94, 35c2c05261d6f6d84aaa1355afa201d507943e76, 3f5e74b5db9353b01ed50f4de84e75b755f8fbc2, 6f072daefcab1d84ce37c073645615f63be91006, 4cf2768a0291a0cdd0dae801ea0eafa3878a349d, d45ff441b416d4aa1af72b1db23d959601c04da2 |
| Linux | Linux Kernel | 2.6.39 up to, but not including, 6.6.136; 6.7 up to, but not including, 6.12.83; 6.13 up to, but not including, 6.18.24; 6.19 up to, but not including, 6.19.14; 7.0 up to, but not including, 7.0.1 | 6.6.136, 6.12.83, 6.18.24, 6.19.14, 7.0.1 |
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: ocfs2: fix use-after-free in ocfs2_fault() when VM_FAULT_RETRY filemap_fault() may drop the mmap_lock before returning VM_FAULT_RETRY, as documented in mm/filemap.c: "If our return value has VM_FAULT_RETRY set, it's because the mmap_lock may be dropped before doing I/O or by lock_folio_maybe_drop_mmap()." When this happens, a concurrent munmap() can call remove_vma() and free the vm_area_struct via RCU. The saved 'vma' pointer in ocfs2_fault() then becomes a dangling pointer, and the subsequent trace_ocfs2_fault() call dereferences it -- a use-after-free. Fix this by saving ip_blkno as a plain integer before calling filemap_fault(), and removing vma from the trace event. Since ip_blkno is copied by value before the lock can be dropped, it remains valid regardless of what happens to the vma or inode afterward.
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.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/4cf2768a0291a0cdd0dae801ea0eafa3878a349d
- git.kernel.org/stable/c/6f072daefcab1d84ce37c073645615f63be91006
- git.kernel.org/stable/c/76a602fdbb78dd05b2da06f74a988cebc97e82d0
- git.kernel.org/stable/c/7de554cabf160e331e4442e2a9ad874ca9875921
- git.kernel.org/stable/c/925bf22c1b823e231b1baea761fe8a1512e442f2
- git.kernel.org/stable/c/d45ff441b416d4aa1af72b1db23d959601c04da2
Other references
Recent Use After Free vulnerabilities
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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