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Linux KernelOperating system · Linux

CVE-2026-45858

MEDIUM · 5.5 CVSS v3.1 Published 2026-05-27
Fix available
A fix is available. Upgrade to 3.3 / 3.5 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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 when it calls ext4_split_extent_at() for the second time, allowing it to properly handle the split. If the split is successful, it will keep extent from 0 to A as unwritten.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 3.2.33, < 3.3>= 3.4.16, < 3.5>= 3.6.4, < 3.7>= 3.7.1, < 6.6.130>= 6.7, < 6.12.75>= 6.13, < 6.18.14>= 6.19, < 6.19.4= 3.7

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 3.3 / 3.5 / 3.7 or later
Fixed in 3.33.53.7
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux kernel >= 6.6.130 (or vendor backport applying commit 1bf6974822d1dba86cf11b5f05498581cf3488a2)

  1. Identify the current running kernel version using 'uname -r'
  2. Determine if the system is running a kernel version affected by CVE-2026-45858 (versions < 6.6.130 for the 6.x branch, or < 3.3, < 3.5, < 3.7, or < 3.7.1 depending on the older branch)
  3. For production systems: schedule a maintenance window for kernel upgrade
  4. Upgrade to Linux kernel >= 6.6.130, or apply the vendor-supplied backport patch for your distribution
  5. The specific upstream fix commit is: 1bf6974822d1dba86cf11b5f05498581cf3488a2
  6. After upgrade, reboot the system to load the patched kernel
  7. Verify the fix is applied by checking the kernel version and confirming ext4 module is loaded
Caveat Kernel upgrades may require system reboot and could have compatibility implications with custom modules or specific hardware drivers; ensure compatibility testing in non-production environment first

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,600. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-45858 in production — separate from our analysis above.

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