CyberSecBulletin
CVE-2024-49924NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2024-49924 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 e657fa2df4429f3805a9b3e47fb1a4a1b02a72bd, 6d0a07f68b66269e167def6c0b90a219cd3e7473, e6897e299f57b103e999e62010b88e363b3eebae 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 0.28% 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 e657fa2df4429f3805a9b3e47fb1a4a1b02a72bd or 6d0a07f68b66269e167def6c0b90a219cd3e7473 or e6897e299f57b103e999e62010b88e363b3eebae or 4cda484e584be34d55ee17436ebf7ad11922b97a, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 4.19.323 or 5.4.285 or 5.10.227 or 5.15.168, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux9f17f2874834f4cdbe48cc05676d8f7558793204 up to, but not including, e657fa2df4429f3805a9b3e47fb1a4a1b02a72bd; 9f17f2874834f4cdbe48cc05676d8f7558793204 up to, but not including, 6d0a07f68b66269e167def6c0b90a219cd3e7473; 9f17f2874834f4cdbe48cc05676d8f7558793204 up to, but not including, e6897e299f57b103e999e62010b88e363b3eebae; 9f17f2874834f4cdbe48cc05676d8f7558793204 up to, but not including, 4cda484e584be34d55ee17436ebf7ad11922b97a; 9f17f2874834f4cdbe48cc05676d8f7558793204 up to, but not including, 3c0d416eb4bef705f699213cee94bf54b6acdacd; 9f17f2874834f4cdbe48cc05676d8f7558793204 up to, but not including, fdda354f60a576d52dcf90351254714681df4370; 9f17f2874834f4cdbe48cc05676d8f7558793204 up to, but not including, aaadc0cb05c999ccd8898a03298b7e5c31509b08; 9f17f2874834f4cdbe48cc05676d8f7558793204 up to, but not including, a3a855764dbacbdb1cc51e15dc588f2d21c93e0e; and 2 more rangese657fa2df4429f3805a9b3e47fb1a4a1b02a72bd, 6d0a07f68b66269e167def6c0b90a219cd3e7473, e6897e299f57b103e999e62010b88e363b3eebae, 4cda484e584be34d55ee17436ebf7ad11922b97a, 3c0d416eb4bef705f699213cee94bf54b6acdacd, fdda354f60a576d52dcf90351254714681df4370
DebianDebian Linux11.0Not stated
LinuxLinux Kernel2.6.27 up to, but not including, 4.19.323; 4.20 up to, but not including, 5.4.285; 5.5 up to, but not including, 5.10.227; 5.11 up to, but not including, 5.15.168; 5.16 up to, but not including, 6.1.113; 6.2 up to, but not including, 6.6.55; 6.7 up to, but not including, 6.10.14; 6.11 up to, but not including, 6.11.34.19.323, 5.4.285, 5.10.227, 5.15.168, 6.1.113, 6.6.55

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.

Scoring systemScoreSeverityScored by
CVSS 3.17.8HighCNA
CVSS 3.17.8HighNVD

Official description

In the Linux kernel, the following vulnerability has been resolved: fbdev: pxafb: Fix possible use after free in pxafb_task() In the pxafb_probe function, it calls the pxafb_init_fbinfo function, after which &fbi->task is associated with pxafb_task. Moreover, within this pxafb_init_fbinfo function, the pxafb_blank function within the &pxafb_ops struct is capable of scheduling work. If we remove the module which will call pxafb_remove to make cleanup, it will call unregister_framebuffer function which can call do_unregister_framebuffer to free fbi->fb through put_fb_info(fb_info), while the work mentioned above will be used. The sequence of operations that may lead to a UAF bug is as follows: CPU0 CPU1 | pxafb_task pxafb_remove | unregister_framebuffer(info) | do_unregister_framebuffer(fb_info) | put_fb_info(fb_info) | // free fbi->fb | set_ctrlr_state(fbi, state) | __pxafb_lcd_power(fbi, 0) | fbi->lcd_power(on, &fbi->fb.var) | //use fbi->fb Fix it by ensuring that the work is canceled before proceeding with the cleanup in pxafb_remove. Note that only root user can remove the driver at runtime.

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

Third-party and government advisories

Recent Use After Free vulnerabilities

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