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CVE Record

CVE-2026-45999: erofs: fix unsigned underflow in z_erofs_lz4_handle_overlap()

In the Linux kernel, the following vulnerability has been resolved: erofs: fix unsigned underflow in z_erofs_lz4_handle_overlap() Some crafted images can have illegal (!partial_decoding && m_llen < m_plen) extents, and the LZ4 inplace decompression path can be wrongly hit, but it cannot handle (outpages < inpages) properly: "outpages - inpages" wraps to a large value and the subsequent rq->out[] access reads past the decompressed_pages array. However, such crafted cases can correctly result in a corruption report in the normal LZ4 non-inplace path. Let's add an additional check to fix this for backporting. Reproducible image (base64-encoded gzipped blob): H4sIAJGR12kCA+3SPUoDQRgG4MkmkkZk8QRbRFIIi9hbpEjrHQI5ghfwCN5BLCzTGtLbBI+g dilSJo1CnIm7GEXFxhT6PDDwfrs73/ywIQD/1ePD4r7Ou6ETsrq4mu7XcWfj++Pb58nJU/9i PNtbjhan04/9GtX4qVYc814WDqt6FaX5s+ZwXXeq52lndT6IuVvlblytLMvh4Gzwaf90nsvz 2DF/21+20T/ldgp5s1jXRaN4t/8izsy/OUB6e/Qa79r+JwAAAAAAAL52vQVuGQAAAP6+my1w ywAAAAAAAADwu14ATsEYtgBQAAA= $ mount -t erofs -o cache_strategy=disabled foo.erofs /mnt $ dd if=/mnt/data of=/dev/null bs=4096 count=1

HighCVSS 7.1Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A crafted EROFS filesystem image can trigger an out-of-bounds kernel read during LZ4 decompression. A user or process must cause the image to be accessed. Successful triggering could expose kernel memory or crash the system, affecting confidentiality and availability.

Executive priority

Prioritize systems that ingest removable, downloaded, tenant-supplied, or otherwise untrusted filesystem images. Patch through supported distribution channels promptly. Exposure is lower where EROFS is unused or image sources are tightly controlled, but kernel-level confidentiality and availability impact justify near-term action.

Technical view

Illegal EROFS extents can incorrectly enter the LZ4 in-place decompression path when output pages are fewer than input pages. Unsigned subtraction wraps to a large value, leading to access beyond the decompressed_pages array. The kernel fix adds a guard so malformed cases follow the corruption-reporting path.

Likely exposure

Systems using affected Linux kernels are potentially exposed when they mount or process untrusted, LZ4-compressed EROFS images. The supplied record lists affected releases from 5.13 through 7.1, but its duplicated hashes and unusual version entries make precise distribution-level mapping uncertain.

Exploitation context

The CVSS vector indicates local access, low complexity, no privileges, and required user interaction. The supplied record includes a reproducer, confirming triggerability. It does not establish practical data recovery or reliable denial of service. KEV is false, and no supplied source reports active exploitation.

Researcher notes

The source assigns CVSS 7.1 with high confidentiality and availability impact, but provides no CWE or CPE mapping. The affected-version data contains repeated commit hashes and an anomalous “0” entry. Validate branch-specific applicability through vendor advisories and the cited stable commits rather than relying only on version strings.

Mitigation direction

  • Install vendor kernel updates that incorporate the applicable referenced stable-kernel fix.
  • Reboot into the updated kernel after installation.
  • Restrict mounting or processing of untrusted EROFS filesystem images until updates are applied.
  • Consult distribution guidance for exact fixed package versions and backport status.

Validation and detection

  • Inventory running kernel versions and systems that mount or process EROFS images.
  • Compare distribution changelogs or patch provenance with the referenced stable-kernel commits.
  • Confirm the updated kernel is running after reboot.
  • Review kernel logs for EROFS corruption reports or related crashes, without treating them as proof of exploitation.
Prepared
Confidence
medium
Sources
9

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-2026-45999 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.1 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/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
8Source 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
7.1CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H1.85.2Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.1High
CVSS 3.1 vector shape for CVE-2026-45999Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/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
LinuxLinux598162d050801e556750defff4ddab499e5d76ed, 598162d050801e556750defff4ddab499e5d76ed, 598162d050801e556750defff4ddab499e5d76ed, 598162d050801e556750defff4ddab499e5d76ed, 598162d050801e556750defff4ddab499e5d76ed, 598162d050801e556750defff4ddab499e5d76ed, 598162d050801e556750defff4ddab499e5d76edunaffected
LinuxLinux5.13, 0, 5.15.210, 6.1.176, 6.6.140, 6.12.88, 6.18.30, 7.0.4, 7.1affected
Weakness

CWE details

No CWE listed

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