CVE-2026-97598

Published Sep 25, 2026

Description

In the Linux kernel, the following vulnerability has been resolved: ipv4: fib: bound automatic table ID allocation fib_empty_table() probes every table ID from 1 until it finds a free one. IPv4 tables are stored in a 256-bucket hash table, so a dense set of IDs makes each probe walk a growing hash chain while RTNL is held. Automatic table assignment ("ip rule ... table 0") is an IPv4-only legacy path. Bound the automatically allocated ID to 4096 so the RTNL hold stays bounded, without changing lookups of explicitly specified table IDs. This changes user-visible behavior. A table-0 rule previously received the lowest free ID in 1..RT_TABLE_MAX (0xFFFFFFFF). After this patch the search stops at 4096 and the rule add fails with ENOBUFS if that range is fully occupied. Explicit table IDs above 4096 remain usable. The automatic path is unused in practice: it is IPv4-only, not documented by ip-rule, uncovered by kernel selftests, and both NetworkManager and systemd refuse table 0.

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References

Frequently Asked Questions

What is CVE-2026-97598? +
In the Linux kernel, the following vulnerability has been resolved: ipv4: fib: bound automatic table ID allocation fib_empty_table() probes every table ID from 1 until it finds a free one. IPv4 tables are stored in a 256-bucket hash table, so a dense set of IDs makes each probe walk a growing hash chain while RTNL is held. Automatic table assignment ("ip rule ... table 0") is an IPv4-only legacy path. Bound the automatically allocated ID to 4096 so the RTNL hold stays bounded, without changing lookups of explicitly specified table IDs. This changes user-visible behavior. A table-0 rule previously received the lowest free ID in 1..RT_TABLE_MAX (0xFFFFFFFF). After this patch the search stops at 4096 and the rule add fails with ENOBUFS if that range is fully occupied. Explicit table IDs above 4096 remain usable. The automatic path is unused in practice: it is IPv4-only, not documented by ip-rule, uncovered by kernel selftests, and both NetworkManager and systemd refuse table 0.
How do I check if I'm vulnerable to CVE-2026-97598? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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