PatchSiren cyber security CVE debrief

CVE-2024-47699 Siemens CVE debrief

A NULL pointer dereference vulnerability exists in the Linux kernel's nilfs2 filesystem driver, specifically within the nilfs_btree_insert() function. The issue arises when a corrupted nilfs2 filesystem image presents an inconsistent b-tree structure: a b-tree root node with height greater than 2 (level > 1) but zero child nodes. Under these conditions, nilfs_btree_do_lookup() fails to initialize path[x].bp_bh buffer head pointers, leaving them NULL. Subsequently, nilfs_btree_get_nonroot_node() attempts to dereference these NULL pointers when accessing buffer memory, triggering a kernel crash. This vulnerability was discovered by syzbot and affects systems mounting potentially corrupted nilfs2 filesystems. The fix adds validation to nilfs_btree_root_broken() to detect this structural inconsistency during root node read operations.

Vendor: Siemens
Product: RUGGEDCOM RST2428P (6GK6242-6PA00)
CVSS: MEDIUM 5.5
CISA KEV: Not listed in stored evidence
Original CVE published: 2024-04-09
Original CVE updated: 2026-05-14
Advisory published: 2024-04-09
Advisory updated: 2026-05-14

Who should care

Linux system administrators managing nilfs2 filesystems, industrial control system operators using Siemens SINEC OS products with nilfs2 support, and security teams responsible for kernel-level vulnerability management in environments where filesystem integrity cannot be guaranteed.

Technical summary

The nilfs2 filesystem driver in the Linux kernel contains a NULL pointer dereference vulnerability in nilfs_btree_insert() when handling corrupted filesystem images. The b-tree lookup logic fails to initialize buffer head pointers when the root node has zero children, but subsequent code attempts to access these NULL pointers when the root level exceeds 1. The vulnerability is triggered during filesystem mount or write operations on affected images. The resolution adds validation to nilfs_btree_root_broken() to detect and reject structurally inconsistent root nodes before they can trigger the dereference.

Defensive priority

medium

Recommended defensive actions

Apply kernel updates from your Linux distribution that include the nilfs2 patch series fixing empty b-tree node handling
Validate nilfs2 filesystem images before mounting using fsck.nilfs2 or similar filesystem checking tools
Implement filesystem integrity monitoring to detect corruption before mount operations
Restrict mount privileges for nilfs2 filesystems to trusted administrative accounts
Monitor kernel logs for nilfs2-related errors that may indicate filesystem corruption attempts

Evidence notes

The vulnerability description indicates this issue was discovered by syzbot and affects corrupted nilfs2 filesystem images. The root cause is a missing sanity check when reading b-tree root nodes with inconsistent height/child-count properties. The fix was implemented as part of a three-patch series addressing empty b-tree node issues.

Official resources

2025-08-12