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CVE Record

CVE-2026-64053: block: don't overwrite bip_vcnt in bio_integrity_copy_user()

In the Linux kernel, the following vulnerability has been resolved: block: don't overwrite bip_vcnt in bio_integrity_copy_user() bio_integrity_add_page() already sets bip_vcnt to 1 for the bounce segment. Overwriting it with nr_vecs breaks bip_vcnt <= bip_max_vcnt on WRITE (bip_max_vcnt is 1), so the gap-merge checks in block/blk.h read past the bip_vec[] flex array. On READ the read is in bounds but lands on a saved user bvec instead of the bounce. The line was added for split propagation, but bio_integrity_clone() doesn't copy bip_vcnt and BIP_CLONE_FLAGS excludes BIP_COPY_USER.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This Linux kernel flaw is a local privilege-risk issue in block-layer integrity handling. A low-privileged local user may be able to trigger memory corruption or incorrect memory access, with CVSS impact marked high for confidentiality, integrity, and availability. It is not listed as actively exploited in the provided sources.

Executive priority

Treat as high priority for Linux fleets where untrusted users, containers, shared hosting, or local code execution exist. It is less urgent than a remotely exploitable bug, but kernel-level impact justifies prompt patch planning.

Technical view

bio_integrity_copy_user() overwrites bip_vcnt after bio_integrity_add_page() sets it to one for a bounce segment. On WRITE this violates bip_vcnt <= bip_max_vcnt and gap-merge checks can read past the bip_vec[] flexible array. On READ, access stays in bounds but references a saved user bvec instead of the bounce buffer.

Likely exposure

Exposure is likely limited to Linux systems running affected kernel versions or downstream builds containing the vulnerable block-layer code. The source bundle identifies Linux kernel affected version data, but does not map exposure to specific distributions, appliances, cloud images, or configurations.

Exploitation context

The CVSS vector is local, low complexity, low privileges required, and no user interaction. The provided KEV flag is false, and the bundle contains no cited evidence of public exploitation, exploit code, or observed attacks.

Researcher notes

The core condition is a bip_vcnt accounting error around copied integrity payloads. The source explains divergent WRITE and READ behavior, but does not provide distribution status, proof-of-concept details, or runtime prerequisites beyond local privileged context from CVSS.

Mitigation direction

  • Apply kernel updates containing the referenced stable fixes.
  • Check Linux distribution advisories for package-specific fixed versions.
  • Prioritize multi-user Linux systems and hosts allowing untrusted local code.
  • Reboot into the fixed kernel after patch installation.
  • Use vendor guidance if live patching is available.

Validation and detection

  • Inventory running kernel versions across Linux hosts.
  • Compare installed kernels against vendor advisories and referenced stable commits.
  • Confirm hosts rebooted into the patched kernel, not only installed it.
  • Review local user and workload exposure on unpatched systems.
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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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CVE-2026-64053 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
0ADP providers
5Source 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: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-2026-64053Attack 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.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux3991657ae7074c3c497bf095093178bed37ea1b4, 3991657ae7074c3c497bf095093178bed37ea1b4, 3991657ae7074c3c497bf095093178bed37ea1b4, 3991657ae7074c3c497bf095093178bed37ea1b4unaffected
LinuxLinux6.11, 0, 6.12.92, 6.18.34, 7.0.11, 7.1affected
Weakness

CWE details

No CWE listed

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