VulnerabilityPublished 27 May 2026Updated 30 Oct 2026

CVE-2026-45985: Linux kernel · ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O

Source GCVE Database

Authoritative record:CVE-2026-45985· High

Not known to be exploited · CVSS 5.5 High · fixed in feaf2a80e78f89ee8a3464126077ba8683b62791 : patch Linux kernel soon.

Data as of 30 Oct 2026, 16:33 UTC

CVSS 3.1 base score

5.5High

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

Patch: Available – fixed in feaf2a80e78f89ee8a3464126077ba8683b62791, 37555690f39f78ef69af347d9aff897e07445949, 2698731d25823267c29190cb578da9296a0c0d7b +5

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

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 27 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-qwcw-8jc7-8mhw

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ b8a8684502a0fc852afa0056c6bb2a9273f6fcc0, < feaf2a80e78f89ee8a3464126077ba8683b62791	Fixed in feaf2a80e78f89ee8a3464126077ba8683b62791
LinuxLinux	Affected ≥ b8a8684502a0fc852afa0056c6bb2a9273f6fcc0, < 37555690f39f78ef69af347d9aff897e07445949	Fixed in 37555690f39f78ef69af347d9aff897e07445949
LinuxLinux	Affected ≥ b8a8684502a0fc852afa0056c6bb2a9273f6fcc0, < 2698731d25823267c29190cb578da9296a0c0d7b	Fixed in 2698731d25823267c29190cb578da9296a0c0d7b
LinuxLinux	Affected ≥ b8a8684502a0fc852afa0056c6bb2a9273f6fcc0, < 2920ec61c98b9476781359f05b94da84e80f54d4	Fixed in 2920ec61c98b9476781359f05b94da84e80f54d4
LinuxLinux	Affected ≥ b8a8684502a0fc852afa0056c6bb2a9273f6fcc0, < 716e7439a5a9b18c3ff882c2f8c834b9ced1aaec	Fixed in 716e7439a5a9b18c3ff882c2f8c834b9ced1aaec
LinuxLinux	Affected ≥ b8a8684502a0fc852afa0056c6bb2a9273f6fcc0, < 77e407967cd872cd75d7e4a691908e49c8e6b4d4	Fixed in 77e407967cd872cd75d7e4a691908e49c8e6b4d4

Description

In the Linux kernel, the following vulnerability has been resolved: ext4: don't set EXT4_GET_BLOCKS_CONVERT when splitting before submitting I/O When allocating blocks during within-EOF DIO and writeback with dioread_nolock enabled, EXT4_GET_BLOCKS_PRE_IO was set to split an existing large unwritten extent. However, EXT4_GET_BLOCKS_CONVERT was set when calling ext4_split_convert_extents(), which may potentially result in stale data issues. Assume we have an unwritten extent, and then DIO writes the second half. [UUUUUUUUUUUUUUUU] on-disk extent U: unwritten extent [UUUUUUUUUUUUUUUU] extent status tree |<- ->| ----> dio write this range First, ext4_iomap_alloc() call ext4_map_blocks() with EXT4_GET_BLOCKS_PRE_IO, EXT4_GET_BLOCKS_UNWRIT_EXT and EXT4_GET_BLOCKS_CREATE flags set. ext4_map_blocks() find this extent and call ext4_split_convert_extents() with EXT4_GET_BLOCKS_CONVERT and the above flags set. Then, ext4_split_convert_extents() calls ext4_split_extent() with EXT4_EXT_MAY_ZEROOUT, EXT4_EXT_MARK_UNWRIT2 and EXT4_EXT_DATA_VALID2 flags set, and it calls ext4_split_extent_at() to split the second half with EXT4_EXT_DATA_VALID2, EXT4_EXT_MARK_UNWRIT1, EXT4_EXT_MAY_ZEROOUT and EXT4_EXT_MARK_UNWRIT2 flags set. However, ext4_split_extent_at() failed to insert extent since a temporary lack -ENOSPC. It zeroes out the first half but convert the entire on-disk extent to written since the EXT4_EXT_DATA_VALID2 flag set, but left the second half as unwritten in the extent status tree. [0000000000SSSSSS] data S: stale data, 0: zeroed [WWWWWWWWWWWWWWWW] on-disk extent W: written extent [WWWWWWWWWWUUUUUU] extent status tree Finally, if the DIO failed to write data to the disk, the stale data in the second half will be exposed once the cached extent entry is gone. Fix this issue by not passing EXT4_GET_BLOCKS_CONVERT when splitting an unwritten extent before submitting I/O, and make ext4_split_convert_extents() to zero out the entire extent range to zero for this case, and also mark the extent in the extent status tree for consistency.

References

Community reviews

Loading reviews…