Description
In the Linux kernel, the following vulnerability has been resolved:

net/sched: act_ct: don't WARN on benign flow_offload_alloc() failure

flow_offload_alloc() returns NULL when the conntrack entry is dying
(e.g. raced with a conntrack flush) or when the GFP_ATOMIC allocation
fails; both are expected under load and neither is a kernel bug. This
path runs from softirq on every committed packet, so with
panic_on_warn=1 an unprivileged user can panic the box just by racing
a conntrack flush against a `tc ... action ct commit` classifier.

Reproduced with a custom repro under QEMU: a small, fixed set of UDP
flows through `tc filter ... action ct commit` on lo, raced against
threads flooding bare ctnetlink CT_DELETE (flush) requests. Hits
WARNING: net/sched/act_ct.c:437 (tcf_ct_flow_table_add(), inlined
into tcf_ct_act() in this build) within ~15s on the unpatched kernel;
same setup is clean on the patched kernel. The fix itself is
behavior-preserving: both branches already did `goto err_alloc`
before and after, only the WARN is removed.
Published: 2026-10-18
Score: n/a
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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History

Sun, 18 Oct 2026 18:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-362
CWE-455

Sun, 18 Oct 2026 15:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: net/sched: act_ct: don't WARN on benign flow_offload_alloc() failure flow_offload_alloc() returns NULL when the conntrack entry is dying (e.g. raced with a conntrack flush) or when the GFP_ATOMIC allocation fails; both are expected under load and neither is a kernel bug. This path runs from softirq on every committed packet, so with panic_on_warn=1 an unprivileged user can panic the box just by racing a conntrack flush against a `tc ... action ct commit` classifier. Reproduced with a custom repro under QEMU: a small, fixed set of UDP flows through `tc filter ... action ct commit` on lo, raced against threads flooding bare ctnetlink CT_DELETE (flush) requests. Hits WARNING: net/sched/act_ct.c:437 (tcf_ct_flow_table_add(), inlined into tcf_ct_act() in this build) within ~15s on the unpatched kernel; same setup is clean on the patched kernel. The fix itself is behavior-preserving: both branches already did `goto err_alloc` before and after, only the WARN is removed.
Title net/sched: act_ct: don't WARN on benign flow_offload_alloc() failure
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-10-18T15:19:42.514Z

Reserved: 2026-09-25T10:25:14.360Z

Link: CVE-2026-98622

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-18T16:17:15.117

Modified: 2026-10-18T16:17:15.117

Link: CVE-2026-98622

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-18T18:30:14Z

Weaknesses