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CVE-2026-99285EUVD-2026-121397

netfilter: nft_byteorder: remove multi-register support

Exploited
No known exploitation
Fix
Fixed in 4.20, 5.5, 5.11, 5.16, 6.2, and 2 more
Who is exposed
Not reported

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

Published
Last modified
Reference
Last checked
20/100 · provisional
None on Exploit-DB, Metasploit or GitHub

Summary

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:

Show the full description

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.

cve.now Index

20Pcve.now Index 20 of 100 · methodology v3 · provisional
  • Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
  • Exposure?/25Unknown. No advisory context yet
  • Reach20/20Affects Linux kernel (software on nearly every server, desktop or phone)
  • Severity?/10Unknown. No CVSS score or vendor rating
  • No patch0/5No signal

What would change the score

  • Would score about 75 if added to CISA KEV
  • Would score about 70 if CISA's SSVC rates exploitation active
  • Would score about 42 if advisories confirm default setups are exposed

How the score works · Rankings

What to do

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

Check your systems with an agent

Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.

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.

Timeline

  1. CVE published
  2. First seen by cve.now

Affected versions

  • 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

    6.7

Evidence 5

CVE record · 2

Establishes: The identifier and description.

  1. Record
  2. Record

Other links · 3

  1. Link
  2. Link
  3. Link

Corrections

None so far.

Something wrong on this page? Report an error. Every fix is listed here.

Questions about CVE-2026-99285

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: cve.now feed data

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: cve.now feed data

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: cve.now feed data

Sources

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