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Medium severity5.5NVD Advisory· Published Feb 27, 2025· Updated May 12, 2026

CVE-2025-21765

CVE-2025-21765

Description

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

ipv6: use RCU protection in ip6_default_advmss()

ip6_default_advmss() needs rcu protection to make sure the net structure it reads does not disappear.

AI Insight

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

Missing RCU protection in ip6_default_advmss() in the Linux kernel's IPv6 stack can lead to a use-after-free, potentially allowing local privilege escalation or denial of service.

The vulnerability resides in the Linux kernel's IPv6 networking code, specifically in the function ip6_default_advmss(). This function reads data from the net structure without proper RCU (Read-Copy-Update) synchronization, meaning the structure could be freed while it is being accessed. This race condition can result in a use-after-free bug.

To exploit this issue, an attacker must have local access to the system and be able to trigger the vulnerable code path. The exact prerequisites are not detailed, but the lack of RCU protection suggests that the vulnerability may be triggered during network operations that involve IPv6 path MTU discovery. The bug can be triggered without requiring high privileges.

If exploited, a use-after-free can lead to memory corruption, system crashes (denial of service), or potentially privilege escalation. The severity is rated medium with a CVSS score of 5.5, indicating a moderate impact on confidentiality, integrity, and availability.

The vulnerability has been fixed in the Linux kernel by adding the necessary RCU read locks. Siemens has also acknowledged the issue in their product security advisory SSA-265688 [1] and SSA-082556 [2], listing the affected SIMATIC S7-1500 products. Users are advised to apply kernel updates or follow the remediation steps provided by Siemens.

References
  1. SSA-265688
  2. SSA-082556

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

245

Patches

0

No patches discovered yet.

Vulnerability mechanics

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References

12

News mentions

0

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