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PatchSiren cyber security CVE debrief

CVE-2026-45857 Linux CVE debrief

A null pointer dereference vulnerability exists in the Linux kernel's Chelsio FCoE driver (csiostor). The flaw occurs in an error exit path where a NULL pointer `rn` is dereferenced via the `CSIO_INC_STATS` macro. The vulnerability was resolved by introducing a separate error return path label after the macro's use, preventing the null dereference. Multiple stable kernel branches received backported fixes.

Vendor
Linux
Product
Unknown
CVSS
MEDIUM 5.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-27
Original CVE updated
2026-06-25
Advisory published
2026-05-27
Advisory updated
2026-06-25

Who should care

Organizations running Linux systems with Chelsio FCoE network adapters utilizing the csiostor driver; kernel maintainers and distribution security teams responsible for stable kernel updates

Technical summary

The csiostor driver in the Linux kernel, which provides SCSI over FCoE (Fibre Channel over Ethernet) support for Chelsio network adapters, contains a null pointer dereference vulnerability. In an error handling path, when pointer `rn` is NULL, the code incorrectly falls through to a path that invokes `CSIO_INC_STATS(rn)`, causing a dereference of the null pointer. The fix introduces a dedicated error return label positioned after the statistics macro usage, ensuring that NULL `rn` cases exit without triggering the dereference. The vulnerability affects systems using Chelsio FCoE hardware with the csiostor driver loaded.

Defensive priority

medium

Recommended defensive actions

  • Apply kernel updates containing the referenced stable branch commits for affected Linux distributions
  • Verify csiostor driver is not in use on systems where FCoE functionality is not required, and consider disabling if unused
  • Monitor distribution security advisories for kernel package updates addressing this CVE
  • Review system logs for any csiostor-related errors that may indicate trigger conditions

Evidence notes

The vulnerability description indicates a null pointer dereference in the csiostor SCSI driver, specifically in error handling code. The fix involves restructuring error paths to avoid dereferencing a NULL `rn` pointer through the `CSIO_INC_STATS` macro. Eight kernel.org stable branch commits are referenced, indicating backports across multiple kernel versions.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-45857 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-45857

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

  • CVE-2026-45857 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-45857

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

Supplemental references

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/16ccbfddcb32365138c806cf572e69b42a193c5c

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/1982257570b84dc33753d536dd969fd357a014e9

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/25ab5e97d3c5f3ed594b4a65d1cc99dc24756681

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/25d623f0d77c11a256a54e860d00c239aa9a2583

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/3bbbab7b6949c76df64210348adbefedaabbf549

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/44ef9f81392de885883f73b9f5c43936a82ae9d7

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/526ea3c0ccd495b0079db3e28fdddd51c1bf01f7

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

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.