CVE-2025-38691

Published Sep 4, 2025

Last updated 4 days ago

CVSS medium 5.5

Overview

Description
In the Linux kernel, the following vulnerability has been resolved: pNFS: Fix uninited ptr deref in block/scsi layout The error occurs on the third attempt to encode extents. When function ext_tree_prepare_commit() reallocates a larger buffer to retry encoding extents, the "layoutupdate_pages" page array is initialized only after the retry loop. But ext_tree_free_commitdata() is called on every iteration and tries to put pages in the array, thus dereferencing uninitialized pointers. An additional problem is that there is no limit on the maximum possible buffer_size. When there are too many extents, the client may create a layoutcommit that is larger than the maximum possible RPC size accepted by the server. During testing, we observed two typical scenarios. First, one memory page for extents is enough when we work with small files, append data to the end of the file, or preallocate extents before writing. But when we fill a new large file without preallocating, the number of extents can be huge, and counting the number of written extents in ext_tree_encode_commit() does not help much. Since this number increases even more between unlocking and locking of ext_tree, the reallocated buffer may not be large enough again and again.
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Modified
Products
linux_kernel, debian_linux

Risk scores

CVSS 3.1

Type
Primary
Base score
5.5
Impact score
3.6
Exploitability score
1.8
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Severity
MEDIUM

Weaknesses

nvd@nist.gov
CWE-908

Social media

Hype score
Not currently trending

  1. [CVE Analysis] CVE-2025-38691: Memory Corruption Chain in Siemens SIMATIC CN 4100 Threatens Communication Node Availability https://t.co/DHRDoDh0Z7 #ICS #OTSecurity #SCADA #CriticalInfrastructure

    @breachspider

    16 Jul 2026

    39 Impressions

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  2. CVE-2025-38691 In the Linux kernel, the following vulnerability has been resolved: pNFS: Fix uninited ptr deref in block/scsi layout The error occurs on the third attempt to encod… https://t.co/OR2ELlrzXH

    @CVEnew

    4 Sept 2025

    75 Impressions

    0 Retweets

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Configurations

Related CVEs

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References

Sources include official advisories and independent security research.