CVE-2026-52999: In the Linux kernel, the following vulnerability has been resolved: netfilter: nfnetlink_osf: fix out-of-boun

Q: How do I fix CVE-2026-52999?

linux kernel: upgrade to 4.20, 5.0, 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, 6.18.33, 7.0.10. Exact commands for each OS are on this page.

Q: Is CVE-2026-52999 being exploited?

CVE-2026-52999 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-52999 affect?

CVE-2026-52999 affects linux kernel. Severity is critical (CVSS 9.1). In the Linux kernel, the following vulnerability has been resolved: netfilter: nfnetlink_osf: fix out-of-bounds read on option matching In nf_osf_match(), the nf_osf_hdr_ctx structure is initialized once and passed by reference to nf_osf_

Q: How urgent is CVE-2026-52999?

Priority 54/100. Critical severity; Remotely exploitable, no login, no user action; On your watchlist

This month

CRITICAL 9.1REMOTEWATCHLISTUPGRADE

CVE-2026-52999 is a critical-severity flaw (CVSS 9.1) affecting linux kernel. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In the Linux kernel, the following vulnerability has been resolved: netfilter: nfnetlink_osf: fix out-of-bounds read on option matching In nf_osf_match(), the nf_osf_hdr_ctx structure is initialized once and passed by reference to nf_osf_match_one() for each fingerprint checked. During TCP option parsing, nf_osf_match_one() advances the shared ctx->optp pointer. If a fingerprint perfectly matches, the function returns early without restoring c

Why this priority

Critical severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 52%)
CISA exploited list	No
Weakness	CWE-125
Published	2026-06-24
Last modified	2026-10-19

Publisher (CNA): kernel.org · Vendor: linux

Last updated 2026-10-19 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-24 17:17 UTCPublished CVE record published
2026-10-19 20:18 UTCUpdated Record last modified

linux linux kernel UPGRADE

Affected: >= 4.19.26 and < 4.20 · >= 4.20.13 and < 5.0 · >= 5.0.1 and < 5.10.258 · >= 5.11 and < 5.15.209 · >= 5.16 and < 6.1.175 · >= 6.2 and < 6.6.141 · >= 6.7 and < 6.12.91 · >= 6.13 and < 6.18.33

Fixed in: 4.20, 5.0, 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, 6.18.33, 7.0.10

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-52999?

linux kernel: upgrade to 4.20, 5.0, 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, 6.18.33, 7.0.10. Exact commands for each OS are on this page.

Is CVE-2026-52999 being exploited?

CVE-2026-52999 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-52999 affect?

CVE-2026-52999 affects linux kernel. Severity is critical (CVSS 9.1). In the Linux kernel, the following vulnerability has been resolved: netfilter: nfnetlink_osf: fix out-of-bounds read on option matching In nf_osf_match(), the nf_osf_hdr_ctx structure is initialized once and passed by reference to nf_osf_

How urgent is CVE-2026-52999?

Priority 54/100. Critical severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Linux kernel vulnerabilities

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References

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