CyberSecBulletin
CVE-2026-63826NVD status: Analyzed

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-63826 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 3047319e44f1368370f6fa2c04dea2961fb10215, 5267eab88fa4c684459504b8be577ad64953b9a6, c6765f39ed27014ff877b00a2efa494233404e17 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.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 3047319e44f1368370f6fa2c04dea2961fb10215 or 5267eab88fa4c684459504b8be577ad64953b9a6 or c6765f39ed27014ff877b00a2efa494233404e17 or 0d35f9f194a858567a21017d69318a51e3a822b9, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.1.191 or 6.6.144 or 6.12.95 or 6.18.38, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 3047319e44f1368370f6fa2c04dea2961fb10215; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 5267eab88fa4c684459504b8be577ad64953b9a6; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, c6765f39ed27014ff877b00a2efa494233404e17; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 0d35f9f194a858567a21017d69318a51e3a822b9; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 70f1e000b88cfa8ca3fd7f4d082647fc089a7769; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 up to, but not including, 2c1c805c65fb7dc7524e20376d6987721e73a0b1; 2.6.123047319e44f1368370f6fa2c04dea2961fb10215, 5267eab88fa4c684459504b8be577ad64953b9a6, c6765f39ed27014ff877b00a2efa494233404e17, 0d35f9f194a858567a21017d69318a51e3a822b9, 70f1e000b88cfa8ca3fd7f4d082647fc089a7769, 2c1c805c65fb7dc7524e20376d6987721e73a0b1
LinuxLinux Kernel2.6.12.1 up to, but not including, 6.1.191; 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; 2.6.126.1.191, 6.6.144, 6.12.95, 6.18.38, 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 NVD.

Official description

In the Linux kernel, the following vulnerability has been resolved: fbdev: fix use-after-free in store_modes() store_modes() replaces a framebuffer's modelist with modes from userspace. On success it frees the old modelist with fb_destroy_modelist(). Two fields still point into that freed list. One pointer is fb_display[i].mode, the mode a console is using. fbcon_new_modelist() moves these pointers to the new list. It only does so for consoles still mapped to the framebuffer. An unmapped console is skipped and keeps its stale pointer. Unbinding fbcon, for example, sets con2fb_map[i] to -1 but leaves fb_display[i].mode set. An FBIOPUT_VSCREENINFO ioctl with FB_ACTIVATE_INV_MODE later reaches fbcon_mode_deleted(). That function reads the stale fb_display[i].mode through fb_mode_is_equal(). The read is a use-after-free. The other pointer is fb_info->mode, the current mode. It is set through the mode sysfs attribute. store_modes() does not update fb_info->mode, so it is left pointing into the freed list. show_mode(), the attribute's read handler, dereferences the stale fb_info->mode through mode_string(). The read is a use-after-free. Clear both pointers before freeing the list. Commit a1f305893074 ("fbcon: Set fb_display[i]->mode to NULL when the mode is released") added the helper fbcon_delete_modelist(). It clears every fb_display[i].mode that points into a given list. So far it is called only from the unregister path. Call it from store_modes() too, and set fb_info->mode to NULL.

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.

More Use After Free vulnerabilities (CWE-416)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Use After Free vulnerabilities

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