Vulnerability in Linux kernel (CVE-2026-45858)
Summary
Vulnerability in Linux kernel (CVE-2026-45858). 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:
ext4: don't zero the entire extent if EXT4_EXT_DATA_PARTIAL_VALID1
When allocating initialized blocks from a large unwritten extent, or
when splitting an unwritten extent during end I/O and converting it to
initialized, there is currently a potential issue of stale data if the
extent needs to be split in the middle.
0 A B N
[UUUUUUUUUUUU] U: unwritten extent
[--DDDDDDDD--] D: valid data
|<- ->| ----> this range needs to be initialized
ext4_split_extent() first try to split this extent at B with
EXT4_EXT_DATA_ENTIRE_VALID1 and EXT4_EXT_MAY_ZEROOUT flag set, but
ext4_split_extent_at() failed to split this extent due to temporary lack
of space. It zeroout B to N and mark the entire extent from 0 to N
as written.
0 A B N
[WWWWWWWWWWWW] W: written extent
[SSDDDDDDDDZZ] Z: zeroed, S: stale data
ext4_split_extent() then try to split this extent at A with
EXT4_EXT_DATA_VALID2 flag set. This time, it split successfully and left
a stale written extent from 0 to A.
0 A B N
[WW|WWWWWWWWWW]
[SS|DDDDDDDDZZ]
Fix this by pass EXT4_EXT_DATA_PARTIAL_VALID1 to ext4_split_extent_at()
when splitting at B, don't convert the entire extent to written and left
it as unwritten after zeroing out B to N. The remaining work is just
like the standard two-part split. ext4_split_extent() will pass the
EXT4_EXT_DATA_VALID2 flag…
Source: GitHub Security Advisories (Global) 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-2026-45858 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-2026-45858" on the vendor's site.
CVE-2026-45858 (Linux kernel) — 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 (unclassified) 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-2026-45858 linux-lts
- Debian DEBIAN-CVE-2026-45858 linux
- Ubuntu UBUNTU-CVE-2026-45858 linux
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