CyberSecBulletin
CVE-2026-31663NVD status: Modified

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-31663 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 4d06caedea587c59cc2cc893ceecc57c75c64312, 94439cbe478b53f92223da9aae95fffb28623c3f, 4236c30b437b80f673b9e08c8fae38b8d471ac9e 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 0.22% 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 4d06caedea587c59cc2cc893ceecc57c75c64312 or 94439cbe478b53f92223da9aae95fffb28623c3f or 4236c30b437b80f673b9e08c8fae38b8d471ac9e or 0f451b43c88bf2b9c038b414be580efee42e031b, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 3.3 or 3.17 or 4.15 or 6.18.23, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxacf568ee859f098279eadf551612f103afdacb4e up to, but not including, 4d06caedea587c59cc2cc893ceecc57c75c64312; acf568ee859f098279eadf551612f103afdacb4e up to, but not including, 94439cbe478b53f92223da9aae95fffb28623c3f; acf568ee859f098279eadf551612f103afdacb4e up to, but not including, 4236c30b437b80f673b9e08c8fae38b8d471ac9e; acf568ee859f098279eadf551612f103afdacb4e up to, but not including, 0f451b43c88bf2b9c038b414be580efee42e031b; acf568ee859f098279eadf551612f103afdacb4e up to, but not including, 5002beda5cac69d522dc54da0d5d463ed9c963d2; acf568ee859f098279eadf551612f103afdacb4e up to, but not including, 1c428b03840094410c5fb6a5db30640486bbbfcb; 69895c5ea0ca2e8d7de1e6d36965d0ab9730787f; 833760100588acfb267dac4d6a02ab9931237739; and 5 more ranges4d06caedea587c59cc2cc893ceecc57c75c64312, 94439cbe478b53f92223da9aae95fffb28623c3f, 4236c30b437b80f673b9e08c8fae38b8d471ac9e, 0f451b43c88bf2b9c038b414be580efee42e031b, 5002beda5cac69d522dc54da0d5d463ed9c963d2, 1c428b03840094410c5fb6a5db30640486bbbfcb
Red HatRed Hat Enterprise Linux 10Not specified in the recordNot stated
Red HatRed Hat Enterprise Linux 8Not specified in the recordNot stated
Red HatRed Hat Enterprise Linux 9Not specified in the recordNot stated
Red HatRed Hat Enterprise Linux 6Not specified in the recordNot stated
Red HatRed Hat Enterprise Linux 7Not specified in the recordNot stated
LinuxLinux Kernel3.2.100 up to, but not including, 3.3; 3.16.55 up to, but not including, 3.17; 4.14.24 up to, but not including, 4.15; 4.15.1 up to, but not including, 6.18.23; 6.19 up to, but not including, 6.19.13; 4.15; 7.03.3, 3.17, 4.15, 6.18.23, 6.19.13

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.

Scoring systemScoreSeverityScored by
CVSS 3.17.8HighCNA
CVSS 3.17.0HighCNA

Official description

In the Linux kernel, the following vulnerability has been resolved: xfrm: hold dev ref until after transport_finish NF_HOOK After async crypto completes, xfrm_input_resume() calls dev_put() immediately on re-entry before the skb reaches transport_finish. The skb->dev pointer is then used inside NF_HOOK and its okfn, which can race with device teardown. Remove the dev_put from the async resumption entry and instead drop the reference after the NF_HOOK call in transport_finish, using a saved device pointer since NF_HOOK may consume the skb. This covers NF_DROP, NF_QUEUE and NF_STOLEN paths that skip the okfn. For non-transport exits (decaps, gro, drop) and secondary async return points, release the reference inline when async is set.

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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