Vulnerability in Linux kernel (CVE-2026-63988)
Summary
Vulnerability in Linux kernel (CVE-2026-63988). 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:
bridge: Fix sleep in atomic context in sysfs path
Since the start of the git history, brport_store() always acquired the
bridge lock. Back then this decision made sense: The bridge lock
protects the STP state of the bridge and its ports and at that time the
function was only used by two STP related attributes (cost and
priority).
Nowadays, brport_store() processes a lot more attributes and most of
them do not need the bridge lock:
-
Bridge flags: Only require RTNL. Read locklessly by the data path.
Annotations can be added in net-next. -
FDB port flushing: Only requires the FDB lock.
-
Multicast attributes: Only require the multicast lock.
-
Group forward mask: Only requires RTNL. Read locklessly by the data
path. Annotations can be added in net-next. -
Backup port: Only requires RTNL. Read locklessly by the data path.
This is a problem as the bridge calls dev_set_promiscuity() when certain
bridge port flags change and this function can sleep since the commit
cited below, resulting in a splat such as [1].
Fix this by reducing the scope of the bridge lock and only take it when
processing the two STP related attributes that require it. Remove the
now stale comment from br_switchdev_set_port_flag(). The
SWITCHDEV_F_DEFER flag can be removed in net-next.
[1]
BUG: sleeping function called from invalid context at net/core/dev_addr_lists.c:1262
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 37…
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-2026-63988 has been found in Linux kernel.
Risk of unauthorized operations or information disclosure. CVSS score: 5.5/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-63988" on the vendor's site.
CVE-2026-63988 (Linux kernel) — CWE-667 / CVSS v3 5.5
Attack vector: local / no user interaction
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 (CWE-667) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: Medium (CVSS 5.5/10). 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。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- BellSoft Alpaquita BELL-CVE-2026-63988 linux-lts Fixed in: 6.18.35-r1
- Ubuntu UBUNTU-CVE-2026-63988 linux-hwe-edge
References
- advisory nvd.nist.gov
- advisory github.com
- package git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web github.com