CyberSecBulletin
CVE-2022-49085NVD status: Analyzed

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2022-49085 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 0489700bfeb1e53eb2039c2291c67e71b0b40103, dcf6be17b5c53b741898d2223b23e66d682de300, 188fe6b26765edbad4055611c0f788b6870f4024 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 0489700bfeb1e53eb2039c2291c67e71b0b40103 or dcf6be17b5c53b741898d2223b23e66d682de300 or 188fe6b26765edbad4055611c0f788b6870f4024 or b6a4055036eed1f5e239ce3d8b0db1ce38bba447, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 4.9.311 or 4.14.276 or 4.19.238 or 5.4.189, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxa29728463b254ce81ecefdf20c1a02e01d9361da up to, but not including, 0489700bfeb1e53eb2039c2291c67e71b0b40103; a29728463b254ce81ecefdf20c1a02e01d9361da up to, but not including, dcf6be17b5c53b741898d2223b23e66d682de300; a29728463b254ce81ecefdf20c1a02e01d9361da up to, but not including, 188fe6b26765edbad4055611c0f788b6870f4024; a29728463b254ce81ecefdf20c1a02e01d9361da up to, but not including, b6a4055036eed1f5e239ce3d8b0db1ce38bba447; a29728463b254ce81ecefdf20c1a02e01d9361da up to, but not including, 594205b4936771a250f9d141e7e0fff21c3dd2d9; a29728463b254ce81ecefdf20c1a02e01d9361da up to, but not including, a972c768723359ec995579902473028fe3cd64b1; a29728463b254ce81ecefdf20c1a02e01d9361da up to, but not including, de63e74da2333b4068bb79983e632db730fea97e; a29728463b254ce81ecefdf20c1a02e01d9361da up to, but not including, 226e993c39405292781bfcf4b039a8db56aab362; and 2 more ranges0489700bfeb1e53eb2039c2291c67e71b0b40103, dcf6be17b5c53b741898d2223b23e66d682de300, 188fe6b26765edbad4055611c0f788b6870f4024, b6a4055036eed1f5e239ce3d8b0db1ce38bba447, 594205b4936771a250f9d141e7e0fff21c3dd2d9, a972c768723359ec995579902473028fe3cd64b1
LinuxLinux Kernel4.5 up to, but not including, 4.9.311; 4.10 up to, but not including, 4.14.276; 4.15 up to, but not including, 4.19.238; 4.20 up to, but not including, 5.4.189; 5.5 up to, but not including, 5.10.111; 5.11 up to, but not including, 5.15.34; 5.16 up to, but not including, 5.16.20; 5.17 up to, but not including, 5.17.3; and 1 more ranges4.9.311, 4.14.276, 4.19.238, 5.4.189, 5.10.111, 5.15.34

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 CISA (ADP).

Official description

In the Linux kernel, the following vulnerability has been resolved: drbd: Fix five use after free bugs in get_initial_state In get_initial_state, it calls notify_initial_state_done(skb,..) if cb->args[5]==1. If genlmsg_put() failed in notify_initial_state_done(), the skb will be freed by nlmsg_free(skb). Then get_initial_state will goto out and the freed skb will be used by return value skb->len, which is a uaf bug. What's worse, the same problem goes even further: skb can also be freed in the notify_*_state_change -> notify_*_state calls below. Thus 4 additional uaf bugs happened. My patch lets the problem callee functions: notify_initial_state_done and notify_*_state_change return an error code if errors happen. So that the error codes could be propagated and the uaf bugs can be avoid. v2 reports a compilation warning. This v3 fixed this warning and built successfully in my local environment with no additional warnings. v2: https://lore.kernel.org/patchwork/patch/1435218/

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

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