Medium [CVE-2026-63968] fix possible infinite loop in fib6_select_path
This medium-severity Red Hat Linux advisory covers CVE-2026-63968 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 fib6_select_path() Found while auditing the same pattern Sashiko reported in rt6_fill_node() [1].
Writers holding tb6_lock can list_del_rcu(&first->fib6_siblings) without waiting for RCU readers; first->fib6_siblings.next then still points into the old ring and this softirq-side walker never reaches &first->fib6_siblings as its terminator. fib6_purge_rt() always WRITE_ONCE()s first->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 stack.
A local attacker could trigger an infinite loop within the `fib6_select_path()` function. This occurs when a writer removes an entry from a list without proper synchronization with readers, causing the list traversal to never terminate.
This vulnerability can lead to a denial of service (DoS) condition, making the system unresponsive. 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.
Affected products named by the advisory: Red Hat package: kernel.
- < 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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