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. Red Hat severity: Moderate — CVSS 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).
Weakness: CWE-835. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 9.
Will not fix / out of support: Red Hat Enterprise Linux 6. Red Hat does not currently list a fixing RHSA for this CVE.
- < 20260526020227.4857-1
Official advisory · high-confidence parse· fetched 8 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 8 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · high-confidence parse· fetched 8 days ago·verify at source
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