ipv4: fib: bound automatic table ID allocation

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Summary

CVECVE-2026-97598
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-25 11:17:11 UTC
Updated2026-09-25 11:17:11 UTC
DescriptionIn 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.

Risk And Classification

EPSS: 0.002000000 probability, percentile 0.088250000 (date 2026-09-27)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected b801f54917b7c6e8540f877ee562cd0725e62ebd bc8d01d856db106f284b19961af6112e10c3e3b4 git Not specified
CNA Linux Linux affected b801f54917b7c6e8540f877ee562cd0725e62ebd fe9a906d2bff2d2707bafd6353b5e032a42aeb35 git Not specified
CNA Linux Linux affected b801f54917b7c6e8540f877ee562cd0725e62ebd 2c29c053a6627dc4f12fcfe6b4860bcd9e5d7503 git Not specified
CNA Linux Linux affected b801f54917b7c6e8540f877ee562cd0725e62ebd efdfb1e27a3328085b79540dfe781d537b576ea1 git Not specified
CNA Linux Linux affected 2.6.19 Not specified
CNA Linux Linux unaffected 2.6.19 semver Not specified
CNA Linux Linux unaffected 6.12.111 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.53 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.7 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/efdfb1e27a3328085b79540dfe781d537b576ea1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fe9a906d2bff2d2707bafd6353b5e032a42aeb35 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/bc8d01d856db106f284b19961af6112e10c3e3b4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2c29c053a6627dc4f12fcfe6b4860bcd9e5d7503 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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