# CVE-2026-93261: locking/lockdep: Fix NULL pointer dereference in __lock_set_class()

CVE-2026-93261 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-93261, released September 24, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-93261
- Priority: Routine
- CVSS: 4.7 (Moderate)
- EPSS: 0.0020
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 24, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-93261

## Description

In the Linux kernel, the following vulnerability has been resolved:  locking/lockdep: Fix NULL pointer dereference in __lock_set_class()  register_lock_class() can return NULL when the lock class pool is exhausted, graph_lock() fails, or key validation fails. However, __lock_set_class() uses the return value directly in pointer arithmetic without a NULL check:    class = register_lock_class(lock, subclass, 0);   hlock->class_idx = class - lock_classes;  If class is NULL, this computes a wild offset that corrupts hlock->class_idx. The subsequent reacquire_held_locks() call will invoke hlock_class() with this corrupted index, leading to a NULL or out-of-bounds pointer dereference.  Add the missing NULL check, consistent with how __lock_acquire() already handles this case at the same call site.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.190-1 | [DEBIAN-CVE-2026-93261](https://patchblox.com/security/data/fix/linux/debian-cve-2026-93261.md) | Sep 24, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.111-1 | [DEBIAN-CVE-2026-93261](https://patchblox.com/security/data/fix/linux/debian-cve-2026-93261.md) | Sep 24, 2026 |
| Linux | linux Debian 14 | 7.2.6-1 | [DEBIAN-CVE-2026-93261](https://patchblox.com/security/data/fix/linux/debian-cve-2026-93261.md) | Sep 24, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.111-1~deb12u1 | [DEBIAN-CVE-2026-93261](https://patchblox.com/security/data/fix/linux/debian-cve-2026-93261.md) | Sep 24, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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