CVE-2025-21764

A vulnerability was found in the Linux kernel's IPv6 Neighbor Discovery (NDISC) subsystem, which manages network neighbor information. The issue arises from improper synchronization mechanisms when allocating socket buffers (sk_buff) in the ndisc_alloc_skb() function. Specifically, the function can be called without holding the necessary Read-Copy-Update (RCU) or Routing Netlink (RTNL) locks, leading to a potential use-after-free (UAF) condition. This flaw allows an attacker with local access and low privileges to exploit the race condition, potentially causing system instability or crashes.

Red Hat Product Security has rated this bug as Moderate due to the following:

Difficult to exploit reliably:

• Requires winning a race condition in the kernel.
• No known public PoC or exploitation.
• Might be nondeterministic and hard to control memory reuse.

May not lead to code execution:

• Use After Free doesn’t automatically mean control.
• Many kernel UAFs cause crashes but not privilege escalation or info leaks unless paired with other bugs.

Limited exposure:

• Requires IPv6 to be enabled.
• Possibly depends on attacker having raw socket access or other local privileges.
• Mitigations Like KASLR, SLAB hardening, and SELinux may further reduce practical risk.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.