Medium [CVE-2026-63969] fix possible infinite loop in rt6_fill_node
This medium-severity Red Hat Linux advisory covers CVE-2026-63969 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 9.
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Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: fix possible infinite loop in rt6_fill_node() Sashiko reported this issue [1]. Apply the same fix as commit f8d8ce1b515a ("ipv6: fix possible infinite loop in fib6_info_uses_dev()").
Writers holding tb6_lock can list_del_rcu(&rt->fib6_siblings) without waiting for RCU readers; rt->fib6_siblings.next then still points into the old ring and this softirq-side walker never reaches &rt->fib6_siblings, causing a CPU stall. fib6_del_route() always WRITE_ONCE()s rt->fib6_nsiblings to 0 before list_del_rcu(), so an inside-loop check is a reliable detach signal. [1] A flaw was found in the Linux kernel's IPv6 networking subsystem.
A local attacker could trigger an infinite loop within the `rt6_fill_node()` function. This occurs when a writer removes an entry from a list without proper synchronization, causing a softirq-side process to continuously loop.
The consequence of this vulnerability is a CPU stall, leading to a Denial of Service (DoS) for the system. This vulnerability is rated as Moderate impact because exploitation requires local system access to trigger concurrent IPv6 routing modifications and queries, restricting the blast radius to a localized denial of service.
- < 20260526020227.4857-1
Official advisory · high-confidence parse· fetched 7 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 7 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That does not mean no fix exists. Read the vendor advisory below for the authoritative guidance.
Official advisory · high-confidence parse· fetched 7 days ago·verify at source
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