CyberSecBulletin
CVE-2026-64530NVD status: Analyzed

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-64530 is a critical-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 5ed3d6f85991656667059d3fa5a1d683ac58c447, f42e8134a3a1074b834a574d404352f867ba994a, 447d493034a9cf7bf13a2abac86d0573d907ec2f 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 0.66% chance of exploitation within 30 days, higher than 52% of scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update Linux to 5ed3d6f85991656667059d3fa5a1d683ac58c447 or f42e8134a3a1074b834a574d404352f867ba994a or 447d493034a9cf7bf13a2abac86d0573d907ec2f or e1270e69dcf2c3512c453484178f2e9dc0db3f05, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.15.212 or 6.1.178 or 6.6.145 or 6.12.97, whichever matches your release line, or a later version.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux172ba7d46c202e679f3ccb10264c67416aaeb1c4 up to, but not including, 5ed3d6f85991656667059d3fa5a1d683ac58c447; 0b5b831122fc3789fff75be433ba3e4dd7b779d4 up to, but not including, f42e8134a3a1074b834a574d404352f867ba994a; 73f7da5fd124f2cda9161e2e46114915e6e82e97 up to, but not including, 447d493034a9cf7bf13a2abac86d0573d907ec2f; 3f14b377d01d8357eba032b4cabc8c1149b458b6 up to, but not including, e1270e69dcf2c3512c453484178f2e9dc0db3f05; 3f14b377d01d8357eba032b4cabc8c1149b458b6 up to, but not including, 2140c2f3f2e7b066e1ae616ede8856cafd8015e9; 3f14b377d01d8357eba032b4cabc8c1149b458b6 up to, but not including, e28aedab9488343924d227b5a896faed67ce84d5; 3f14b377d01d8357eba032b4cabc8c1149b458b6 up to, but not including, a8a02897f2b479127db261de05cbf0c28b98d159; f5346df0591d10bc948761ca854b1fae6d2ef441; and 5 more ranges5ed3d6f85991656667059d3fa5a1d683ac58c447, f42e8134a3a1074b834a574d404352f867ba994a, 447d493034a9cf7bf13a2abac86d0573d907ec2f, e1270e69dcf2c3512c453484178f2e9dc0db3f05, 2140c2f3f2e7b066e1ae616ede8856cafd8015e9, e28aedab9488343924d227b5a896faed67ce84d5
LinuxLinux Kernel5.15.148 up to, but not including, 5.15.212; 6.1.75 up to, but not including, 6.1.178; 6.6.14 up to, but not including, 6.6.145; 6.7.2 up to, but not including, 6.12.97; 6.13 up to, but not including, 6.18.40; 6.19 up to, but not including, 7.1.55.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5

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
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
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:N/AC:L/PR:N/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: net/sched: cls_api: Handle TC_ACT_CONSUMED in tcf_qevent_handle tcf_classify() can return TC_ACT_CONSUMED while the skb is held by the defragmentation engine (e.g. act_ct on out-of-order fragments). When that happens the skb is no longer owned by the caller and must not be touched again. tcf_qevent_handle() did not handle TC_ACT_CONSUMED: it fell through the switch and returned the skb to the caller as if classification had passed. The only qdisc that wires up qevents today is RED, via three call sites (qe_mark on RED_PROB_MARK/HARD_MARK, qe_early_drop on congestion_drop) red_enqueue() was continuing to operate on an skb it no longer owns in this case -- enqueueing it, dropping it, or updating statistics. Resulting in a UAF. tc qdisc add dev eth0 root handle 1: red ... qevent early_drop block 10 tc filter add block 10 ... action ct (with ct defrag enabled and traffic that produces out-of-order fragments, e.g. a fragmented UDP stream) Handle TC_ACT_CONSUMED in tcf_qevent_handle() the same way the ingress and egress fast paths do: treat it as stolen and return NULL without touching the skb. Unlike the TC_ACT_STOLEN case, the skb must not be dropped/freed here, as it is no longer owned by us.

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

References

Recent Use After Free vulnerabilities

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