CVE-2025-39946: In the Linux kernel, the following vulnerability has been resolved: tls: make sure to abort the stream if hea

Q: How do I fix CVE-2025-39946?

linux kernel: upgrade to 6.1.154, 6.6.108, 6.12.49, 6.16.9. Exact commands for each OS are on this page.

Q: Is CVE-2025-39946 being exploited?

CVE-2025-39946 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-2025-39946 affect?

CVE-2025-39946 affects linux kernel. Severity is critical (CVSS 9.8). In the Linux kernel, the following vulnerability has been resolved: tls: make sure to abort the stream if headers are bogus Normally we wait for the socket to buffer up the whole record before we service it. If the socket has a tiny buffe

Q: How urgent is CVE-2025-39946?

Priority 76/100. Critical severity; EPSS top 4%: very likely to be exploited; Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action; On your watchlist

This week

CRITICAL 9.8REMOTEWATCHLISTUPGRADE

CVE-2025-39946 is a critical-severity flaw (CVSS 9.8) 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: tls: make sure to abort the stream if headers are bogus Normally we wait for the socket to buffer up the whole record before we service it. If the socket has a tiny buffer, however, we read out the data sooner, to prevent connection stalls. Make sure that we abort the connection when we find out late that the record is actually invalid. Retrying the parsing is fine in itself bu

Why this priority

Critical severity
EPSS top 4%: very likely to be exploited
Public exploit reference
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	10.3% (top 4%)
CISA exploited list	No
Published	2025-10-04
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

2025-10-04 08:15 UTCPublished CVE record published
2026-10-19 21:10 UTCUpdated Record last modified

linux linux kernel UPGRADE

Affected: >= 6.0 and < 6.1.154 · >= 6.2 and < 6.6.108 · >= 6.7 and < 6.12.49 · >= 6.13 and < 6.16.9 · 6.17 rc1 · 6.17 rc2 · 6.17 rc3 · 6.17 rc4

Fixed in: 6.1.154, 6.6.108, 6.12.49, 6.16.9

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.

Exact fixes by distribution

Fedora 46 · wordpress · FIXED · 7.1.4-1.fc46 · FEDORA-2026-907394725e · source

sudo dnf upgrade --advisory=FEDORA-2026-907394725e

Fedora ELN · rhc · FIXED · 0.3.15-1.eln159 · FEDORA-2026-1cd9f35750 · source

sudo dnf upgrade --advisory=FEDORA-2026-1cd9f35750

Debian 12 · linux · FIXED · 6.1.158-1

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "6.1.158-1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · linux · FIXED · 6.12.57-1

sudo apt update && sudo apt install --only-upgrade linux dpkg --compare-versions "$(dpkg-query -W -f='${Version}' linux)" ge "6.12.57-1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 10 · kernel · FIXED · kernel-6.12.0-124.11.1.el10_1

sudo dnf upgrade --advisory=RHSA-2025:21463 rpm -q kernel

RHEL 6 · kernel · NOT AFFECTED

RHEL 7 · kernel · NOT AFFECTED

RHEL 7 · kernel-rt · NOT AFFECTED

RHEL 8 · kernel · NOT AFFECTED

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2025-1254 · source

sudo dnf update --advisory=ALAS2023-2025-1254

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: farazsth98/exploit-CVE-2025-39946 (37 stars)

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-2025-39946?

linux kernel: upgrade to 6.1.154, 6.6.108, 6.12.49, 6.16.9. Exact commands for each OS are on this page.

Is CVE-2025-39946 being exploited?

CVE-2025-39946 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-2025-39946 affect?

CVE-2025-39946 affects linux kernel. Severity is critical (CVSS 9.8). In the Linux kernel, the following vulnerability has been resolved: tls: make sure to abort the stream if headers are bogus Normally we wait for the socket to buffer up the whole record before we service it. If the socket has a tiny buffe

How urgent is CVE-2025-39946?

Priority 76/100. Critical severity; EPSS top 4%: very likely to be exploited; Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Linux kernel vulnerabilities

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References

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