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CVE Record

CVE-2025-40167: ext4: detect invalid INLINE_DATA + EXTENTS flag combination

In the Linux kernel, the following vulnerability has been resolved: ext4: detect invalid INLINE_DATA + EXTENTS flag combination syzbot reported a BUG_ON in ext4_es_cache_extent() when opening a verity file on a corrupted ext4 filesystem mounted without a journal. The issue is that the filesystem has an inode with both the INLINE_DATA and EXTENTS flags set: EXT4-fs error (device loop0): ext4_cache_extents:545: inode #15: comm syz.0.17: corrupted extent tree: lblk 0 < prev 66 Investigation revealed that the inode has both flags set: DEBUG: inode 15 - flag=1, i_inline_off=164, has_inline=1, extents_flag=1 This is an invalid combination since an inode should have either: - INLINE_DATA: data stored directly in the inode - EXTENTS: data stored in extent-mapped blocks Having both flags causes ext4_has_inline_data() to return true, skipping extent tree validation in __ext4_iget(). The unvalidated out-of-order extents then trigger a BUG_ON in ext4_es_cache_extent() due to integer underflow when calculating hole sizes. Fix this by detecting this invalid flag combination early in ext4_iget() and rejecting the corrupted inode.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A corrupted ext4 filesystem can present an inode with two incompatible storage flags. When Linux opens an affected verity file under the described conditions, the kernel can hit a fatal assertion, potentially crashing the system. Systems that mount untrusted or damaged ext4 media face the clearest risk.

Executive priority

Prioritize internet-facing infrastructure platforms, image-processing services, and shared systems that mount untrusted ext4 content. For systems limited to trusted, managed storage, schedule the vendor kernel update through normal expedited patching while monitoring for revised vendor guidance.

Technical view

The incompatible INLINE_DATA and EXTENTS flags bypass extent-tree validation in __ext4_iget(). Out-of-order extents can then cause integer underflow during hole-size calculation and trigger BUG_ON in ext4_es_cache_extent(). The fix rejects the invalid flag combination when loading the inode.

Likely exposure

Exposure requires an affected Linux kernel to process a specially corrupted ext4 filesystem, specifically involving a verity file mounted without a journal. Risk is higher for systems mounting user-controlled images, removable media, or potentially damaged volumes. The supplied affected-version data is ambiguous, so distribution-specific status requires confirmation.

Exploitation context

The bundle identifies syzbot discovery but provides no evidence of malicious exploitation. CVE-2025-40167 is not marked KEV. The CVSS vector describes local access and user interaction; it does not indicate a remotely reachable network attack.

Researcher notes

The described failure most directly supports a kernel crash or denial-of-service condition. Although the supplied CVSS assigns high confidentiality, integrity, and availability impact, the narrative does not explain data disclosure or modification. Exact vulnerable branch boundaries should be verified against vendor advisories and the referenced stable commits.

Mitigation direction

  • Upgrade to a vendor kernel containing the applicable referenced stable fix.
  • Check distribution security guidance for exact affected and fixed package versions.
  • Restrict mounting of untrusted ext4 images or removable filesystems until patched.
  • Avoid affected hosts processing potentially corrupted ext4 volumes where operationally feasible.

Validation and detection

  • Inventory kernel versions and identify systems using or mounting ext4 filesystems.
  • Identify services that accept user-supplied disk images, removable media, or external volumes.
  • Confirm vendor package changelogs reference CVE-2025-40167 or an applicable stable fix commit.
  • In an isolated test environment, confirm invalid inodes are rejected without triggering a kernel BUG.
Prepared
Confidence
medium
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2025-40167 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
0ADP providers
9Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-40167Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxf19d5870cbf72d4cb2a8e1f749dff97af99b071e, f19d5870cbf72d4cb2a8e1f749dff97af99b071e, f19d5870cbf72d4cb2a8e1f749dff97af99b071e, f19d5870cbf72d4cb2a8e1f749dff97af99b071e, f19d5870cbf72d4cb2a8e1f749dff97af99b071e, f19d5870cbf72d4cb2a8e1f749dff97af99b071e, f19d5870cbf72d4cb2a8e1f749dff97af99b071e, f19d5870cbf72d4cb2a8e1f749dff97af99b071eunaffected
LinuxLinux3.8, 0, 5.4.301, 5.10.246, 5.15.196, 6.1.158, 6.6.114, 6.12.55, 6.17.5, 6.18affected
Weakness

CWE details

No CWE listed

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