What’s Vulnerable › Vulnerabilities

CVE-2025-38588: ipv6: prevent infinite loop in rt6_nlmsg_size()

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-08-19 · updated 2026-06-17
• Weakness: CWE-835

Description

In the Linux kernel, the following vulnerability has been resolved: ipv6: prevent infinite loop in rt6_nlmsg_size() While testing prior patch, I was able to trigger an infinite loop in rt6_nlmsg_size() in the following place: list_for_each_entry_rcu(sibling, &f6i->fib6_siblings, fib6_siblings) { rt6_nh_nlmsg_size(sibling->fib6_nh, &nexthop_len); } This is because fib6_del_route() and fib6_add_rt2node() uses list_del_rcu(), which can confuse rcu readers, because they might no longer see the head of the list. Restart the loop if f6i->fib6_nsiblings is zero.

Affected products

• Debian Linux: 11.0
• Linux kernel: from 6.1.128 before 6.1.148; from 6.6.75 before 6.6.102; from 6.11.11 before 6.12; from 6.12.2 before 6.12.42; from 6.13 before 6.15.10; from 6.16 before 6.16.1 — fixed in 6.1.148, 6.12, 6.12.42, 6.15.10, 6.16.1, 6.6.102

How to fix

Upgrade to a fixed version: Linux kernel 6.1.148, 6.12, 6.12.42, 6.15.10. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/3c13db3e47e170bab19e574404e7b6be45ea873d
• https://git.kernel.org/stable/c/46aeb66e9e54ed0d56c18615e1c3dbd502b327ab
• https://git.kernel.org/stable/c/54e6fe9dd3b0e7c481c2228782c9494d653546da
• https://git.kernel.org/stable/c/6d345136c9b875f065d226908a29c25cdf9343f8
• https://git.kernel.org/stable/c/cd8d8bbd9ced4cc5d06d858f67d4aa87745e8f38
• https://git.kernel.org/stable/c/e1b7932af47f92432be8303d2439d1bf77b0be23
• https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html

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