Junglewise Threat Intelligence

CVE-2025-38708: Linux Kernel use after free in DRBD handle_write_conflicts

CVE-2025-38708 · Severity: critical · CVSS 9.8 · Published 2025-09-04

Technologies: Linux Kernel, Siemens SIMATIC CN 4100, Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP. Vendors: Linux, Siemens.

Executive brief

A vulnerability exists in the Linux kernel's Distributed Replicated Block Device (DRBD) driver, which is used to mirror storage between servers for high availability. Under specific configurations where two servers are allowed to write simultaneously, a software error can cause the system to crash or allow unauthorized memory access. This could lead to service outages or potential data corruption in environments using older DRBD versions for clustered storage or live virtual machine migration.

Technical details

A use-after-free (UAF) vulnerability exists in the Linux kernel DRBD driver (drivers/block/drbd/drbd_receiver.c) due to a missing reference count increment (kref_get) in the 'handle_write_conflicts' function. When the 'two-primaries' feature is enabled and concurrent writes occur, the driver may prematurely call 'drbd_destroy_device', leading to a UAF condition and subsequent kernel panic. While the vendor notes this path is rarely triggered in production due to upper-layer locking (DLM), an attacker capable of generating specific network-based write conflicts could trigger the flaw. Patches have been released for multiple stable kernel branches including 4.19, 5.4, 5.10, 5.15, 6.1, 6.6, 6.10, and 6.11.

Affected products

  • Linux Linux Kernel versions prior to 6.15 (stable branches 4.19.y, 5.4.y, 5.10.y, 5.15.y, 6.1.y, 6.6.y, 6.10.y, 6.11.y)
  • Siemens SIMATIC CN 4100 versions prior to V5.0
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5 and later

Timeline

  • 2025-06-27: patched: Initial patch authored
  • 2025-09-04: advisory: CVE-2025-38708 published

References

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