# CVE-2026-97598: Linux kernel denial of service in IPv4 routing table allocation

Source: https://junglewise.ai/threats/cve-2026-97598-in-the-linux-kernel-the-following-vulnerability-has-been-resolved  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-25. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-97598 · Severity: info · Published 2026-09-25

The Linux kernel's IPv4 routing subsystem could be slowed down or made unresponsive due to inefficient searching for available routing table identifiers. When systems automatically assign routing table IDs (a legacy IPv4 feature), the kernel would scan through an increasingly long list while holding a critical networking lock, potentially causing temporary network unavailability during table rule operations.

Technologies: [Linux](https://junglewise.ai/threats/technologies/linux-linux). Vendors: [Linux](https://junglewise.ai/threats/vendors/linux).

## Quick answers

**Is CVE-2026-97598 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-97598 being exploited in the wild.

**How severe is CVE-2026-97598?** Informational severity, published 25 September 2026.

**Which products and versions are affected?** Linux affected versions across the kernel stable tree including 2.6, 3.x, 4.x, 5.x, 6.x, and 7.x series.

**Is there a fix for CVE-2026-97598?** A patch was published on 2026-09-21: Patch merged upstream and backported to stable branches Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-97598 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-97598?** Check whether you run Linux at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The fib_empty_table() function in net/ipv4/fib_rules.c performed unbounded linear search for available routing table IDs from 1 to RT_TABLE_MAX (0xFFFFFFFF) while holding the RTNL lock. With many tables allocated, hash chain traversals grew expensive. The fix bounds automatic table allocation to ID 4096, limiting RTNL hold time without affecting explicit table ID lookups. The automatic path affects only legacy "ip rule ... table 0" usage, which is undocumented and refused by NetworkManager and systemd.

## Affected products

- Linux Linux affected versions across the kernel stable tree including 2.6, 3.x, 4.x, 5.x, 6.x, and 7.x series

## Timeline

- 2026-09-25: disclosed
- 2026-09-21: patched: Patch merged upstream and backported to stable branches

## References

- [https://git.kernel.org/stable/c/2c29c053a6627dc4f12fcfe6b4860bcd9e5d7503](https://git.kernel.org/stable/c/2c29c053a6627dc4f12fcfe6b4860bcd9e5d7503)
- [https://git.kernel.org/stable/c/bc8d01d856db106f284b19961af6112e10c3e3b4](https://git.kernel.org/stable/c/bc8d01d856db106f284b19961af6112e10c3e3b4)

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