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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
Unknown
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-27
Original CVE updated
2026-05-27
Advisory published
2026-05-27
Advisory updated
2026-05-27

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.

Official resources

2026-05-27