Vulnerability in Linux kernel (CVE-2026-90248)
Summary
Vulnerability in Linux kernel (CVE-2026-90248). Risk of unauthorized operations or information disclosure.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
net/sched: cls_api: fix teardown of an adopted proto on insert-race loss
In tc_new_tfilter() the create branch sets tp_created = 1 before calling
tcf_chain_tp_insert_unique(). When the caller loses the race (another
request inserted a proto at the same chain/prio first), insert_unique()
destroys the caller's own tp_new and returns the winner's proto with an
extra reference. tp_created was never cleared, so the loser's errout
path treated the winner's live proto as its own and called
tcf_chain_tp_delete_empty() on it, silently unlinking an active
classifier that the winning request already advertised via
RTM_NEWTFILTER.
Track the outcome of the insert step in a single tri-state variable so
each errout path reacts correctly:
- TP_NOT_CREATED: no proto created; pursue the old path.
- TP_CREATED: proto inserted successfully; same code path as before.
- TP_NOT_OWNED: New - lost the insert race; tp is another request's proto
(chain ref already released by tp_new's destroy)
Both errout reactions are single expressions derived from the state.
This fix is motivated by the Sashiko's automated review of Patch
(net/sched: cls_api: Always acquire rtnl_lock when destroying locked
classifiers) [1][2]. The review identified the silent-unlink behaviour of
an adopted proto's teardown when a request loses the
tcf_chain_tp_insert_unique() race.
[1] https://sashiko.dev/#/patchset/20260801125632.360365-1-jhs%40mojatatu.co…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-90248 has been found in Linux kernel.
Risk of unauthorized operations or information disclosure.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-90248" on the vendor's site.
CVE-2026-90248 (Linux kernel)
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (unclassified) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Ubuntu UBUNTU-CVE-2026-90248 linux-hwe-edge
References
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web nvd.nist.gov
- web github.com