Linux: Use After Free
CVE-2026-63816 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 7d3ae21783e5914c1761ac7d63f882d3d70800e9, 56038756aae68312df00d4aa1d97e51ef3aca725, a499f77c06050a28c897bdbd86cd2f0721ae0743 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 7d3ae21783e5914c1761ac7d63f882d3d70800e9 or 56038756aae68312df00d4aa1d97e51ef3aca725 or a499f77c06050a28c897bdbd86cd2f0721ae0743 or a805fec35c201c59643ddcde713bce4051c8ee27, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.145 or 6.12.96 or 6.18.39 or 7.1.3, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 3db1de0e582c358dd013f3703cd55b5fe4076436 up to, but not including, 7d3ae21783e5914c1761ac7d63f882d3d70800e9; 3db1de0e582c358dd013f3703cd55b5fe4076436 up to, but not including, 56038756aae68312df00d4aa1d97e51ef3aca725; 3db1de0e582c358dd013f3703cd55b5fe4076436 up to, but not including, a499f77c06050a28c897bdbd86cd2f0721ae0743; 3db1de0e582c358dd013f3703cd55b5fe4076436 up to, but not including, a805fec35c201c59643ddcde713bce4051c8ee27; 3db1de0e582c358dd013f3703cd55b5fe4076436 up to, but not including, e0288584baa5dc41df4a829a023c4c1b33fe53d7; 6db52f1944417c2601182a591a704e2f119c5215; 5.18.18 up to, but not including, 5.19; 5.19 | 7d3ae21783e5914c1761ac7d63f882d3d70800e9, 56038756aae68312df00d4aa1d97e51ef3aca725, a499f77c06050a28c897bdbd86cd2f0721ae0743, a805fec35c201c59643ddcde713bce4051c8ee27, e0288584baa5dc41df4a829a023c4c1b33fe53d7, 5.19 |
| Linux | Linux Kernel | 5.18.18 up to, but not including, 6.6.145; 6.7 up to, but not including, 6.12.96; 6.13 up to, but not including, 6.18.39; 6.19 up to, but not including, 7.1.3 | 6.6.145, 6.12.96, 6.18.39, 7.1.3 |
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: f2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode - ioctl(F2FS_IOC_GARBAGE_COLLECT_RANGE) - shrink - f2fs_gc - gc_data_segment - ra_data_block(cow_inode) - mapping = F2FS_I(inode)->atomic_inode->i_mapping : f2fs_is_cow_file(cow_inode) is true - f2fs_evict_inode(atomic_inode) - clear_inode_flag(fi->cow_inode, FI_COW_FILE) - F2FS_I(fi->cow_inode)->atomic_inode = NULL ... - truncate_inode_pages_final(atomic_inode) - f2fs_grab_cache_folio(mapping) : create folio in atomic_inode->mapping - clear_inode(atomic_inode) - BUG_ON(atomic_inode->i_data.nrpages) We need to add a reference on fi->atomic_inode before using its mapping field during garbage collection, otherwise, it will cause UAF issue.
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/56038756aae68312df00d4aa1d97e51ef3aca725
- git.kernel.org/stable/c/7d3ae21783e5914c1761ac7d63f882d3d70800e9
- git.kernel.org/stable/c/a499f77c06050a28c897bdbd86cd2f0721ae0743
- git.kernel.org/stable/c/a805fec35c201c59643ddcde713bce4051c8ee27
- git.kernel.org/stable/c/e0288584baa5dc41df4a829a023c4c1b33fe53d7
Recent Use After Free vulnerabilities
- 8.8 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 7.8 High severity
- 9.8 Critical severity
- 8.8 High severity
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