CVE-2024-26924 Siemens CVE debrief

Who should care

System administrators managing Linux-based network infrastructure, particularly those using nftables for packet filtering and classification; security teams responsible for industrial control systems and operational technology networks using Siemens SCALANCE, RUGGEDCOM, or SINEC OS products; kernel maintainers and developers working with netfilter/nftables implementations; organizations relying on timeout-based nftables sets for dynamic access control or rate limiting.

Technical summary

The vulnerability exists in the nft_set_pipapo.c implementation of the Linux kernel's netfilter framework. The pipapo (Pile of Packets) set type is used for high-performance packet classification with support for timeout-based element expiration. The flaw manifests in the element removal path when: (1) multiple elements exist with identical keys, which occurs when a new element is inserted while an existing same-key element has timed out or is marked inactive for the next generation; (2) the nft_pipapo_remove() function performs a lookup and marks an element inactive; (3) during the second removal step, the function may unmap a different element than the one deactivated, due to insufficient validation that the fully matching key corresponds to the deactivated element. This error leaves the actually-deactivated element reachable in the set structure (stale pointer) while the non-deactivated element becomes unreachable (memory leak). Subsequent lookups retrieving the stale element can trigger kernel crashes. The fix adds explicit verification that the key-to-element mapping matches the deactivated element before proceeding with unmapping, plus bug/warn assertions to catch invalid removal attempts.

Defensive priority

MEDIUM

Recommended defensive actions

• Apply vendor-provided kernel updates to address the nft_set_pipapo use-after-free condition
• For Siemens SINEC OS and affected SCALANCE/RUGGEDCOM products, update to V3.1 or later as specified in vendor security advisory
• Monitor nftables set operations for abnormal patterns involving rapid element addition and removal with short timeouts
• Implement network segmentation to limit exposure of netfilter/nftables interfaces to untrusted networks
• Review and restrict administrative access to nftables configuration to reduce attack surface
• Consider enabling kernel memory sanitizers (KASAN) in test environments to detect similar use-after-free conditions during validation

Evidence notes

The vulnerability description is derived from the Linux kernel commit message resolving the issue, as cited in CISA advisory ICSA-25-226-15 and Siemens ProductCERT SSA-613116. The technical analysis of the two-step removal process and key collision scenario is based on the detailed commit notes provided in the source corpus. CVSS 3.1 vector AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H yields a base score of 5.9 (MEDIUM), reflecting network attack vector but high attack complexity due to the specific timing conditions required.

Sources and references

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.