CVE-2025-40198

Kernel memory disclosure via unterminated mount-options field

Published Nov 12, 2025 · Updated Aug 5, 2026

Buffer over-read in the Linux ext4 driver allows attackers to disclose kernel memory or crash a host via a crafted filesystem image. parse_apply_sb_mount_options() treats the 64-byte s_mount_opts superblock field as NUL-terminated, so string parsing can continue into adjacent kernel memory when no terminator is present. Reaching the flaw requires a user or automounter to mount the supplied image; failed parsing can log over-read bytes, while an unmapped read can oops or panic the host.

CVSS severity7.8
High
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer over-read in the Linux ext4 driver allows attackers to disclose kernel memory or crash a host via a crafted filesystem image. parse_apply_sb_mount_options() treats the 64-byte s_mount_opts superblock field as NUL-terminated, so string parsing can continue into adjacent kernel memory when no terminator is present. Reaching the flaw requires a user or automounter to mount the supplied image; failed parsing can log over-read bytes, while an unmapped read can oops or panic the host.

The record

CVE
CVE-2025-40198
Published
Nov 12, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 12, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.6.36
  2. Affected versionversion=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <01829af7656b56d83682b3491265d583d502e502
  3. Affected versionversion=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <2a0cf438320cdb783e0378570744c0ef0d83e934
  4. Affected versionversion=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <7bf46ff83a0ef11836e38ebd72cdc5107209342d
  5. Affected versionversion=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8
  6. Affected versionversion=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <a6e94557cd05adc82fae0400f6e17745563e5412
  7. Affected versionversion=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <b2bac84fde28fb6a88817b8b761abda17a1d300b
  8. Affected versionversion=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <e651294218d2684302ee5ed95ccf381646f3e5b4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.36; version=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <01829af7656b56d83682b3491265d583d502e502; version=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <2a0cf438320cdb783e0378570744c0ef0d83e934; version=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <7bf46ff83a0ef11836e38ebd72cdc5107209342d; version=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8; version=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <a6e94557cd05adc82fae0400f6e17745563e5412; version=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <b2bac84fde28fb6a88817b8b761abda17a1d300b; version=8b67f04ab9de5d8f3a71aef72bf02c995a506db5 <e651294218d2684302ee5ed95ccf381646f3e5b4

Published CVSS scores

7.8Linux Kernel CVE TeamCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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