The Linux kernel’s IPv6 multicast source filtering routine mutates the source filter list in place while other threads may be reading that list under an RCU read lock. Because 16‑byte IPv6 address writes are not atomic and the array is shifted without synchronization, concurrent readers can observe torn or duplicated address entries. An attacker could generate multicast traffic that triggers these race conditions and cause the kernel to misinterpret source addresses or crash the networking stack, potentially exposing internal IPv6 addresses or disrupting multicast service.

The vulnerability exists in all Linux kernel builds containing the unpatched ip6_mc_source() implementation. Affected vendors include the Linux kernel maintainers; affected versions are those released before the commit that introduced copy‑on‑write RCU updates (e.g., the snapshot before commit 20db91a052332ef5). No specific patch level is listed, so kernels up to the corresponding release are impacted.

The CVSS score is not available and the EPSS score is not reported, indicating no known wide‑scale exploitation. The vulnerability requires simultaneous read/write activity on multicast source filters, which is not trivial to orchestrate from an external entity. Because it is a race condition that leads to corrupted data rather than immediate code execution, the risk is assessed as low to moderate. The vulnerability is not listed in the CISA KEV catalog, and no public exploits have been reported.