Linux Kernel up to 6.18.39/7.1.4/7.2-rc1 iomap iomap_writeback_handle_eof io_size integer underflow

CVSS Meta Temp Score
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CTI Interest Score
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4.2$0-$5k0.00+

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Linux Kernel up to 6.18.39/7.1.4/7.2-rc1. This vulnerability affects the function iomap_writeback_handle_eof of the component iomap. The manipulation of the argument io_size leads to integer underflow. This vulnerability is referenced as CVE-2026-72367. The attack can only be performed from a local environment. No exploit is available.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.18.39/7.1.4/7.2-rc1 and classified as problematic. This issue affects the function iomap_writeback_handle_eof of the component iomap. The manipulation of the argument io_size with an unknown input leads to a integer underflow vulnerability. Using CWE to declare the problem leads to CWE-191. The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result. Impacted is integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: iomap: guard io_size EOF trim against concurrent truncate underflow iomap: fix zero padding data issue in concurrent append writes changed ioend accounting so that io_size tracks only valid data within EOF. This trims io_size when a writeback range extends past end_pos: ioend->io_size += map_len; if (ioend->io_offset + ioend->io_size > end_pos) ioend->io_size = end_pos - ioend->io_offset; However, if end_pos ends up below ioend->io_offset, the subtraction becomes negative and is stored in size_t io_size, causing an unsigned wrap to a huge value. This can happen when writeback continues past byte-level EOF up to a block-aligned range, or when a concurrent truncate shrinks the file after end_pos was sampled in iomap_writeback_handle_eof(). A wrapped io_size can mislead append detection and corrupt completion-time size handling, since filesystem end_io paths consume io_size for decisions such as on-disk EOF updates and unwritten/COW completion ranges. Fix this by clamping io_size to zero when EOF has moved to or before the ioend start offset. This preserves the original intent of trimming io_size to valid in-EOF data while avoiding the underflow.

The advisory is shared at git.kernel.org. The identification of this vulnerability is CVE-2026-72367 since 08/09/2026. The exploitation is known to be easy. An attack has to be approached locally. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/15/2026).

Upgrading to version 6.18.40, 7.1.5 or 7.2-rc2 eliminates this vulnerability. Applying the patch 1f38f65bf965fce9aa159d45c5347538f56c5973/7f7780abb4c0fdc9a2603aea8e985ff14ee900e0/55ec50d046c03b3724741957f7b007856e36dbe7 is able to eliminate this problem.

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Productinfo

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Version

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.4
VulDB Meta Temp Score: 4.2

VulDB Base Score: 4.4
VulDB Temp Score: 4.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Integer underflow
CWE: CWE-191 / CWE-189
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.18.40/7.1.5/7.2-rc2
Patch: 1f38f65bf965fce9aa159d45c5347538f56c5973/7f7780abb4c0fdc9a2603aea8e985ff14ee900e0/55ec50d046c03b3724741957f7b007856e36dbe7

Timelineinfo

08/09/2026 CVE reserved
08/15/2026 +6 days Advisory disclosed
08/15/2026 +0 days VulDB entry created
08/15/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-72367 (🔒)
GCVE (CVE): GCVE-0-2026-72367
GCVE (VulDB): GCVE-100-390965

Entryinfo

Created: 08/15/2026 16:40
Changes: 08/15/2026 16:40 (60)
Complete: 🔍
Cache ID: 216::103

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