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PatchSiren cyber security CVE debrief

CVE-2026-64324 Linux CVE debrief

A local availability issue exists in the Linux kernel due to improper validation of free block extents against the partition length in the UDF filesystem implementation. This can cause a kernel panic when a crafted filesystem image is mounted and a file is truncated. The issue arises from the udf_free_blocks() function, which checks the logical block number and count against the partition length but fails to account for the extent offset. As a result, a crafted extent can pass the guard while logicalBlockNum + offset + count points past the partition, leading to an out-of-bounds read of a bitmap pointer slot followed by a kernel panic. On desktop systems where UDisks/polkit allows

Vendor
Linux
Product
Unknown
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-25
Original CVE updated
2026-10-19
Advisory published
2026-07-25
Advisory updated
2026-10-19

Who should care

Linux system administrators, users with unprivileged local access, and security teams responsible for Linux systems should assess exposure and apply patches or mitigations as needed.

Why it matters

A local availability issue in the Linux kernel's UDF filesystem implementation can cause a kernel panic when a crafted filesystem image is mounted and a file is truncated. Linux system administrators and security teams should assess exposure and apply patches or mitigations as needed.

  • Local unprivileged users can trigger a kernel panic, leading to a denial of service.
  • Systems allowing unprivileged mounting of UDF media are more vulnerable.
  • Verification of affected versions and application of patches is necessary.

Technical summary

The Linux kernel's UDF filesystem implementation does not properly validate free block extents against the partition length. A crafted extent can pass the guard while logicalBlockNum + offset + count points past the partition, which later indexes past the space bitmap array. This results in a kernel panic when a file is truncated on a file system backed by such an extent. The vulnerability is a local availability issue, with no confidentiality or integrity impact claimed. The issue is exploitable by an unprivileged local user on systems allowing unprivileged mounting of UDF media, such as desktop systems with UDisks/polkit enabled.

Defensive priority

High

Recommended defensive actions

  • Review and apply the patches provided by the Linux kernel maintainers.
  • Restrict access to unprivileged local users who can mount removable UDF media.
  • Monitor systems for kernel panics and adjust logging and alerting as needed.
  • Verify affected versions and apply patches or mitigations as needed.
  • Conduct a thorough review of system logs to detect potential exploitation attempts.
  • Implement additional monitoring and detection mechanisms for UDF filesystem usage.
  • Track and document changes to filesystem configurations and user access controls.

Evidence notes

The CVE record and Linux kernel source code indicate a local availability issue due to improper validation of free block extents in the UDF filesystem. No confidentiality or integrity impact is claimed.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-64324 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-64324

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-64324 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-64324

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • udf: validate free block extents against the partition length

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/64xxx/CVE-2026-64324.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/fdd6229d2ae9914c1f25d1041db0f4f312a4fa76

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/b54aee5652fcd7c23a0904a4623ec462c3edc70c

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/12af328d2ee8d68e81ba612246d0b54b22d23e1f

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/fb49099206c5c57af28a157249fa7bcb5518f99e

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/9442d75429b0c556292a7454fe888d54259f5240

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/335202ab25b01fdd45889ff25eab70864686dea3

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/be87de7789a82a030a4896bc7683415ec9fa6f2b

    Supplemental source

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.