Vulnerability in Linux kernel (CVE-2026-97555)
Summary
Vulnerability in Linux kernel (CVE-2026-97555). Successful exploitation can lead to full system takeover.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix heap overflow in DACL owner/group rewrite
When id_mode_to_cifs_acl rewrites an existing DACL, it allocates a
buffer sized according to the on-disk DACL length reported by
dacl_ptr->size. However, replace_sids_and_copy_aces may rewrite each
ACE with a new owner/group SID obtained from the cifs.idmap upcall.
Those SIDs can have up to SID_MAX_SUB_AUTHORITIES (15) sub-authorities,
making each ACE up to 76 bytes (sizeof(struct smb_ace)).
If the original DACL contains short SIDs (e.g., 1 sub-authority) while
the replacement SIDs are long, the rewritten ACEs overflow the
allocation.
Fix this by always budgeting for worst-case SID expansion: allocate
sizeof(struct smb_acl) plus num_aces * sizeof(struct smb_ace), which
covers the smb_acl header and room for every ACE at maximum SID size.
This replaces the previous split logic that used dacl_ptr->size for
cifsacl mounts but num_aces * sizeof(struct smb_ace) for mode_from_sid
mounts: both paths can trigger the same rewrite and need the same
headroom.
KASAN reports this as:
BUG: KASAN: slab-out-of-bounds in build_sec_desc+0x1e8a/0x2680 [cifs]
Write of size 4 at addr ffff8881a5e25374 by task chown/5298
...
The buggy address is located 0 bytes to the right of
allocated 884-byte region [ffff8881a5e25000, ffff8881a5e25374)
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-2026-97555 has been found in Linux kernel.
Successful exploitation can lead to full system takeover. CVSS score: 8.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-97555" on the vendor's site.
CVE-2026-97555 (Linux kernel) — CVSS v3 8.8
Attack vector: remote (network-reachable) / unauthenticated
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: High (CVSS 8.8/10). Successful exploitation can lead to full system takeover.
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
- Debian DEBIAN-CVE-2026-97555 linux
- Ubuntu UBUNTU-CVE-2026-97555 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 git.kernel.org
- web git.kernel.org
- web github.com