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CVE Record

CVE-2024-26704: ext4: fix double-free of blocks due to wrong extents moved_len

In the Linux kernel, the following vulnerability has been resolved: ext4: fix double-free of blocks due to wrong extents moved_len In ext4_move_extents(), moved_len is only updated when all moves are successfully executed, and only discards orig_inode and donor_inode preallocations when moved_len is not zero. When the loop fails to exit after successfully moving some extents, moved_len is not updated and remains at 0, so it does not discard the preallocations. If the moved extents overlap with the preallocated extents, the overlapped extents are freed twice in ext4_mb_release_inode_pa() and ext4_process_freed_data() (as described in commit 94d7c16cbbbd ("ext4: Fix double-free of blocks with EXT4_IOC_MOVE_EXT")), and bb_free is incremented twice. Hence when trim is executed, a zero-division bug is triggered in mb_update_avg_fragment_size() because bb_free is not zero and bb_fragments is zero. Therefore, update move_len after each extent move to avoid the issue.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A flaw in Linux ext4 extent-moving logic can free the same storage blocks twice, corrupt filesystem accounting, and trigger a kernel division-by-zero during trimming. Successful abuse requires local access and low privileges, but the stated potential impact includes confidentiality, integrity, and availability. Systems using affected Linux kernels with ext4 filesystems deserve prompt remediation.

Executive priority

Treat as a high-priority operating-system maintenance issue, especially on shared Linux hosts using ext4. It does not present documented remote or active exploitation, so emergency internet-edge response is unsupported. Patch through normal accelerated kernel maintenance, prioritizing systems with untrusted local users or sensitive data.

Technical view

ext4_move_extents() could leave moved_len at zero after partially successful extent moves. Consequently, inode preallocations were not discarded, allowing overlapping extents to be released twice. This corrupts bb_free accounting; a later trim can reach mb_update_avg_fragment_size() with bb_free nonzero and bb_fragments zero, causing division by zero. Stable kernel commits update moved_len after each move.

Likely exposure

Exposure is limited to Linux systems running an affected kernel and using ext4. The supplied CVSS vector requires local access and low privileges, with no user interaction. The bundle identifies affected releases or branches from 3.18 through 6.8, but its version formatting is insufficient to establish precise downstream distribution package boundaries.

Exploitation context

The supplied record is not in CISA KEV and provides no evidence of active exploitation. The flaw is locally reachable rather than remotely exploitable according to CVSS. Exploitation would depend on affected ext4 extent-moving behavior and overlapping preallocations; the documented failure may surface during filesystem trimming.

Researcher notes

The core condition is stale moved_len after partial success, missed preallocation cleanup, double release, corrupted free-space counters, and a later trim-triggered zero division. Multiple upstream stable commits are supplied, indicating backports across kernel lines. Exact introduction and fixed-version ranges cannot be reconstructed confidently from the bundle’s flattened version list.

Mitigation direction

  • Install a distribution-supported kernel containing the applicable upstream stable fix.
  • Consult the Linux distribution advisory to map packaged kernel versions accurately.
  • Prioritize multi-user systems where untrusted local accounts can access ext4 storage.
  • Reboot into the corrected kernel after installation, following vendor guidance.

Validation and detection

  • Inventory running kernel versions and identify mounted ext4 filesystems.
  • Compare installed kernel packages against distribution advisories and upstream stable fixes.
  • Confirm the running kernel changed after remediation and reboot.
  • Review kernel logs for ext4 errors, division faults, or unexpected trim-related crashes.
  • Verify routine filesystem and trim operations remain healthy after patching.
Prepared
Confidence
medium
Sources
6

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-2024-26704 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:L/UI:N/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
2ADP providers
11Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

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:L/UI:N/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-2024-26704Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/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.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxfcf6b1b729bcd23f2b49a84fb33ffbb44712ee6a, fcf6b1b729bcd23f2b49a84fb33ffbb44712ee6a, fcf6b1b729bcd23f2b49a84fb33ffbb44712ee6a, fcf6b1b729bcd23f2b49a84fb33ffbb44712ee6a, fcf6b1b729bcd23f2b49a84fb33ffbb44712ee6a, fcf6b1b729bcd23f2b49a84fb33ffbb44712ee6a, fcf6b1b729bcd23f2b49a84fb33ffbb44712ee6a, fcf6b1b729bcd23f2b49a84fb33ffbb44712ee6aunaffected
LinuxLinux3.18, 0, 4.19.307, 5.4.269, 5.10.210, 5.15.149, 6.1.79, 6.6.18, 6.7.6, 6.8affected
Weakness

CWE details

No CWE listed

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