net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain (CVE-2026-74740) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-74740

net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain

Answer in brief

CVE-2026-74740 records a Unknown severity vulnerability in net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 26, 2026Updated Aug 26, 2026Source checked Aug 26, 2026First seen by HOL Aug 26, 2026Material review Aug 26, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=ee3bbfe806cdb46b02cda63626cb50a7a7b19fc5 <91d55fd1fdb85c8371ca8793c788ea7d5192383a \|\| >=ee3bbfe806cdb46b02cda63626cb50a7a7b19fc5 <1ec48b6715c29b20105e3485206602cff6c51ae5 \|\| >=ee3bbfe806cdb46b02cda63626cb50a7a7b19fc5 <abceabc4408fca6a9dd52611f5d197dec9390d63 \|\| >=ee3bbfe806cdb46b02cda63626cb50a7a7b19fc5 <6b70886ebc428eed43a069c8944a931b5fb3f4e4 \|\| >=ee3bbfe806cdb46b02cda63626cb50a7a7b19fc5 <f60b396ee174206fe08ebf997d16cd3801b77b22	91d55fd1fdb85c8371ca8793c788ea7d5192383a, 1ec48b6715c29b20105e3485206602cff6c51ae5, abceabc4408fca6a9dd52611f5d197dec9390d63, 6b70886ebc428eed43a069c8944a931b5fb3f4e4, f60b396ee174206fe08ebf997d16cd3801b77b22
Linux/Linuxgeneric	5.1	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to 91d55fd1fdb85c8371ca8793c788ea7d5192383a if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 26, 2026

Sources and claim methodology

Upstream source description

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain tcf_action_exec() handles TC_ACT_GOTO_CHAIN by first checking rcu_access_pointer(a->goto_chain) and then calling tcf_action_goto_chain_exec(), which does a second, independent rcu_dereference_bh(a->goto_chain) read and immediately dereferences chain->filter_chain. A concurrent tcf_action_set_ctrlact() (e.g. the gact replace path) can clear a->goto_chain between the two reads, so the second read returns NULL and tcf_action_goto_chain_exec() dereferences NULL. Fix the race by doing a single rcu_dereference_bh() read of a->goto_chain in tcf_action_exec(), checking it once for NULL, and passing the resulting chain pointer into tcf_action_goto_chain_exec(). This turns the split check/use into a single check/use on one value.

Quoted source text, attributed separately from HOL analysis.