Linux: Use After Free
CVE-2026-63800 is a critical-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 4ad8b9a85dbf57ca532ee9e65ad7e6498bfbbf98, 1f24b8302c77dcaf79c64c073877a3b9f4dd25d2, 9c0fb5c09ae5bd68dc0038692af8127029cb0385 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 0.64% chance of exploitation within 30 days, higher than 51% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to 4ad8b9a85dbf57ca532ee9e65ad7e6498bfbbf98 or 1f24b8302c77dcaf79c64c073877a3b9f4dd25d2 or 9c0fb5c09ae5bd68dc0038692af8127029cb0385 or 7e37e9b3e82ade881e1798e2f4fcc54aff7793c1, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.5 or 5.10.260 or 5.15.211 or 6.1.177, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 06f58dbc49a23c99e5c0f246879ed16667f7bf8f up to, but not including, 4ad8b9a85dbf57ca532ee9e65ad7e6498bfbbf98; 2c8d5fc37fe2384a9bdb6965443ab9224d46f704 up to, but not including, 1f24b8302c77dcaf79c64c073877a3b9f4dd25d2; 2c8d5fc37fe2384a9bdb6965443ab9224d46f704 up to, but not including, 9c0fb5c09ae5bd68dc0038692af8127029cb0385; 2c8d5fc37fe2384a9bdb6965443ab9224d46f704 up to, but not including, 7e37e9b3e82ade881e1798e2f4fcc54aff7793c1; 2c8d5fc37fe2384a9bdb6965443ab9224d46f704 up to, but not including, 2883ddd7542b4437a2ab4908fe2773f690e20889; 2c8d5fc37fe2384a9bdb6965443ab9224d46f704 up to, but not including, 200e7637f4d6a1342987045eea72641524f909dc; 2c8d5fc37fe2384a9bdb6965443ab9224d46f704 up to, but not including, 9645aaf689aff57427ece3b9fa47d5b5399417f4; 2c8d5fc37fe2384a9bdb6965443ab9224d46f704 up to, but not including, 13e198a90ca4050f4bee8a3f23680389a6563ccc; and 4 more ranges | 4ad8b9a85dbf57ca532ee9e65ad7e6498bfbbf98, 1f24b8302c77dcaf79c64c073877a3b9f4dd25d2, 9c0fb5c09ae5bd68dc0038692af8127029cb0385, 7e37e9b3e82ade881e1798e2f4fcc54aff7793c1, 2883ddd7542b4437a2ab4908fe2773f690e20889, 200e7637f4d6a1342987045eea72641524f909dc |
| Linux | Linux Kernel | 5.4.91 up to, but not including, 5.5; 5.10.9 up to, but not including, 5.10.260; 5.11.1 up to, but not including, 5.15.211; 5.16 up to, but not including, 6.1.177; 6.2 up to, but not including, 6.6.144; 6.7 up to, but not including, 6.12.95; 6.13 up to, but not including, 6.18.38; 6.19 up to, but not including, 7.1.3; and 1 more ranges | 5.5, 5.10.260, 5.15.211, 6.1.177, 6.6.144, 6.12.95 |
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
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- 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:N/AC:L/PR:N/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: pNFS: Fix use-after-free in pnfs_update_layout() When hitting the NFS_LAYOUT_RETURN branch in pnfs_update_layout(), the code calls pnfs_prepare_to_retry_layoutget(lo). If it succeeds, pnfs_put_layout_hdr(lo) is called before trace_pnfs_update_layout(), which still references 'lo'. This results in a use-after-free when the tracepoint accesses lo's fields. Fix this by moving the tracepoint call before pnfs_put_layout_hdr(lo).
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: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/13e198a90ca4050f4bee8a3f23680389a6563ccc
- git.kernel.org/stable/c/1f24b8302c77dcaf79c64c073877a3b9f4dd25d2
- git.kernel.org/stable/c/200e7637f4d6a1342987045eea72641524f909dc
- git.kernel.org/stable/c/2883ddd7542b4437a2ab4908fe2773f690e20889
- git.kernel.org/stable/c/4ad8b9a85dbf57ca532ee9e65ad7e6498bfbbf98
- git.kernel.org/stable/c/7e37e9b3e82ade881e1798e2f4fcc54aff7793c1
- git.kernel.org/stable/c/9645aaf689aff57427ece3b9fa47d5b5399417f4
- git.kernel.org/stable/c/9c0fb5c09ae5bd68dc0038692af8127029cb0385
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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