CyberSecBulletin
CVE-2024-39495NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2024-39495 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 74cd0a421896b2e07eafe7da4275302bfecef201, 2b6bb0b4abfd79b8698ee161bb73c0936a2aaf83, fb071f5c75d4b1c177824de74ee75f9dd34123b9 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 0.32% 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 74cd0a421896b2e07eafe7da4275302bfecef201 or 2b6bb0b4abfd79b8698ee161bb73c0936a2aaf83 or fb071f5c75d4b1c177824de74ee75f9dd34123b9 or 9a733d69a4a59c2d08620e6589d823c24be773dc, whichever matches your release line, or a later version.
  2. Update linux_kernel to 74cd0a421896 or 2b6bb0b4abfd or fb071f5c75d4 or 9a733d69a4a5, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux55742d2a071a569bf20f90d37b1b5b8a25a3f882 up to, but not including, 74cd0a421896b2e07eafe7da4275302bfecef201; 55742d2a071a569bf20f90d37b1b5b8a25a3f882 up to, but not including, 2b6bb0b4abfd79b8698ee161bb73c0936a2aaf83; 55742d2a071a569bf20f90d37b1b5b8a25a3f882 up to, but not including, fb071f5c75d4b1c177824de74ee75f9dd34123b9; 55742d2a071a569bf20f90d37b1b5b8a25a3f882 up to, but not including, 9a733d69a4a59c2d08620e6589d823c24be773dc; 55742d2a071a569bf20f90d37b1b5b8a25a3f882 up to, but not including, 0b8fba38bdfb848fac52e71270b2aa3538c996ea; 55742d2a071a569bf20f90d37b1b5b8a25a3f882 up to, but not including, 03ea2b129344152157418929f06726989efc0445; 55742d2a071a569bf20f90d37b1b5b8a25a3f882 up to, but not including, 5c9c5d7f26acc2c669c1dcf57d1bb43ee99220ce; 4.974cd0a421896b2e07eafe7da4275302bfecef201, 2b6bb0b4abfd79b8698ee161bb73c0936a2aaf83, fb071f5c75d4b1c177824de74ee75f9dd34123b9, 9a733d69a4a59c2d08620e6589d823c24be773dc, 0b8fba38bdfb848fac52e71270b2aa3538c996ea, 03ea2b129344152157418929f06726989efc0445
Linuxlinux_kernelbefore 74cd0a421896; 1da177e4c3f4 up to, but not including, 2b6bb0b4abfd; 1da177e4c3f4 up to, but not including, fb071f5c75d4; 1da177e4c3f4 up to, but not including, 9a733d69a4a5; 1da177e4c3f4 up to, but not including, 0b8fba38bdfb; 1da177e4c3f4 up to, but not including, 03ea2b129344; 1da177e4c3f4 up to, but not including, 5c9c5d7f26ac74cd0a421896, 2b6bb0b4abfd, fb071f5c75d4, 9a733d69a4a5, 0b8fba38bdfb, 03ea2b129344

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 3.17.8HighNVD
CVSS 3.17.8HighCISA (ADP)

Official description

In the Linux kernel, the following vulnerability has been resolved: greybus: Fix use-after-free bug in gb_interface_release due to race condition. In gb_interface_create, &intf->mode_switch_completion is bound with gb_interface_mode_switch_work. Then it will be started by gb_interface_request_mode_switch. Here is the relevant code. if (!queue_work(system_long_wq, &intf->mode_switch_work)) { ... } If we call gb_interface_release to make cleanup, there may be an unfinished work. This function will call kfree to free the object "intf". However, if gb_interface_mode_switch_work is scheduled to run after kfree, it may cause use-after-free error as gb_interface_mode_switch_work will use the object "intf". The possible execution flow that may lead to the issue is as follows: CPU0 CPU1 | gb_interface_create | gb_interface_request_mode_switch gb_interface_release | kfree(intf) (free) | | gb_interface_mode_switch_work | mutex_lock(&intf->mutex) (use) Fix it by canceling the work before kfree.

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: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Use After Free vulnerabilities

Spotted an error? Tell us.