CyberSecBulletin
CVE-2026-63823NVD status: Analyzed

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-63823 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 d8274181b0f28d450b42489723a5ba81042158d7, 4982bfabce6b33b3c9eddb4fb900fe5568b7cf91, 708709c65a1832a99b0eef8ae46e343ddaca3d06 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 d8274181b0f28d450b42489723a5ba81042158d7 or 4982bfabce6b33b3c9eddb4fb900fe5568b7cf91 or 708709c65a1832a99b0eef8ae46e343ddaca3d06 or 35ab4db86774d82389e4b9559e26ab7f68d8e395, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.260 or 5.15.211 or 6.1.177 or 6.6.144, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxb5f545c880a2a47947ba2118b2509644ab7a2969 up to, but not including, d8274181b0f28d450b42489723a5ba81042158d7; b5f545c880a2a47947ba2118b2509644ab7a2969 up to, but not including, 4982bfabce6b33b3c9eddb4fb900fe5568b7cf91; b5f545c880a2a47947ba2118b2509644ab7a2969 up to, but not including, 708709c65a1832a99b0eef8ae46e343ddaca3d06; b5f545c880a2a47947ba2118b2509644ab7a2969 up to, but not including, 35ab4db86774d82389e4b9559e26ab7f68d8e395; b5f545c880a2a47947ba2118b2509644ab7a2969 up to, but not including, f9b68632ac93cc742f2e411021c4dbfe452ea0c2; b5f545c880a2a47947ba2118b2509644ab7a2969 up to, but not including, 7216ce8cb12fee44e309503955bb83806b106129; b5f545c880a2a47947ba2118b2509644ab7a2969 up to, but not including, 83c0a1cb296d955d5f4d1f0bd8a769ba8ed8c29f; b5f545c880a2a47947ba2118b2509644ab7a2969 up to, but not including, fd15b457a86939c38aa12116adabd8ff686c5e51; and 1 more rangesd8274181b0f28d450b42489723a5ba81042158d7, 4982bfabce6b33b3c9eddb4fb900fe5568b7cf91, 708709c65a1832a99b0eef8ae46e343ddaca3d06, 35ab4db86774d82389e4b9559e26ab7f68d8e395, f9b68632ac93cc742f2e411021c4dbfe452ea0c2, 7216ce8cb12fee44e309503955bb83806b106129
LinuxLinux Kernel2.6.16 up to, but not including, 5.10.260; 5.11 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, 7.1.35.10.260, 5.15.211, 6.1.177, 6.6.144, 6.12.95, 6.18.38

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 CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: keys: Pin request_key_auth payload in instantiate paths A: request_key() B: KEYCTL_INSTANTIATE_IOV ================ ========================= create auth key store rka in auth key wait for helper get auth key load rka from auth key copy user payload sleep on #PF helper completed detach and free rka destroy auth key wake up use rka->target_key **USE-AFTER-FREE** Give request_key_auth payloads a refcount. Take a payload reference while authkey->sem stabilizes the payload and revocation state. Hold that reference across the instantiate and reject paths. Drop the auth key owning reference from revoke and destroy. [jarkko: Replaced the first two paragraphs of text with an actual concurrency scenario.]

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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