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High severity7.8NVD Advisory· Published Feb 27, 2025· Updated May 12, 2026

CVE-2025-21764

CVE-2025-21764

Description

In the Linux kernel, the following vulnerability has been resolved:

ndisc: use RCU protection in ndisc_alloc_skb()

ndisc_alloc_skb() can be called without RTNL or RCU being held.

Add RCU protection to avoid possible UAF.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

A use-after-free in Linux kernel's ICMPv6 Neighbor Discovery skb allocation due to missing RCU protection is fixed.

Vulnerability

Overview

CVE-2025-21764 is a use-after-free (UAF) vulnerability in the Linux kernel's Neighbor Discovery (NDISC) subsystem. The function ndisc_alloc_skb() could be invoked without the RCU (Read-Copy-Update) lock or RTNL (Routing Netlink) lock held, allowing a race condition where the underlying neighbour data structure could be freed before the allocated socket buffer (skb) was fully initialized [1][2]. This missing RCU protection defeats the kernel's memory safety guarantees for shared data in the networking stack.

Exploitation

Conditions

An attacker with local access and the ability to trigger ICMPv6 neighbor discovery messages (e.g., by crafting specific IPv6 packets or manipulating network state) could exploit this race. No special privileges are required beyond the ability to interact with the IPv6 networking subsystem. The attack surface is limited to systems where the kernel is running a version prior to the inclusion of the fix commit.

Impact

Successful exploitation could allow an attacker to cause a use-after-free, leading to memory corruption, a kernel crash (denial of service), or potentially arbitrary code execution in kernel context. The CVSS v3 score of 7.8 (High) reflects the possibility of high impact on confidentiality, integrity, and availability, though typical exploitation likely results in a denial of service.

Mitigation

Patches have been committed to the Linux kernel stable tree [2][3][4]. Users should update to a kernel version containing the fix (e.g., by applying the relevant stable commit). The vulnerability is also trackable in Siemens product advisories as part of a larger collection of CVEs affecting their SIMATIC S7-1500 TM MFP - GNU/Linux subsystem [1], indicating that affected industrial products require firmware updates.

References
  1. SSA-265688
  2. Making sure you're not a bot!
  3. Making sure you're not a bot!
  4. Making sure you're not a bot!

AI Insight generated on May 20, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

244

Patches

0

No patches discovered yet.

Vulnerability mechanics

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References

11

News mentions

0

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