dbcve.org
Linux KernelOperating system · Linux

CVE-2026-43198

CRITICAL · 9.8 CVSS v3.1 Published 2026-05-06
Fix available
A fix is available. Upgrade to 6.18.16 / 6.19.6 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: tcp: fix potential race in tcp_v6_syn_recv_sock() Code in tcp_v6_syn_recv_sock() after the call to tcp_v4_syn_recv_sock() is done too late. After tcp_v4_syn_recv_sock(), the child socket is already visible from TCP ehash table and other cpus might use it. Since newinet->pinet6 is still pointing to the listener ipv6_pinfo bad things can happen as syzbot found. Move the problematic code in tcp_v6_mapped_child_init() and call this new helper from tcp_v4_syn_recv_sock() before the ehash insertion. This allows the removal of one tcp_sync_mss(), since tcp_v4_syn_recv_sock() will call it with the correct context.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A race condition in tcp_v6_syn_recv_sock() where after tcp_v4_syn_recv_sock() returns, the child socket is already visible in the TCP ehash table and accessible by other CPUs, but newinet->pinet6 still incorrectly points to the listener's ipv6_pinfo instead of the child's, potentially causing memory corruption or use-after-free.

MitigationApply the upstream kernel patch which moves socket initialization code to tcp_v6_mapped_child_init() and calls it before ehash insertion to ensure proper socket context is established before the socket becomes visible to other CPUs.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 2.6.12.1, < 6.18.16>= 6.19, < 6.19.6= 2.6.12= 7.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed kernel version
    Run 'uname -r' or 'cat /proc/version' to get the kernel version
    Affected if The kernel version falls within >= 2.6.12.1 and < 6.18.16, or >= 6.19 and < 6.19.6, or equals 2.6.12, or equals 7.0
  2. Verify IPv6 kernel support is enabled
    Check if the kernel has IPv6 support by running 'lsmod | grep ipv6' or checking /proc/sys/net/ipv6/conf/all/disable_ipv6
    Affected if IPv6 support is loaded or the system has IPv6 interfaces configured (value shows 0)
  3. Confirm the system accepts TCPv6 connections
    Check for listening TCPv6 sockets with 'ss -tlnp | grep -i ":::"' or 'netstat -tlnp | grep -i "::"'
    Affected if The system has TCP sockets listening on IPv6 addresses (:: or ::1)

The system is affected if it runs a kernel version within the affected ranges AND has IPv6 enabled and accepts TCP IPv6 connections, as the race condition occurs in the child socket creation path for TCPv6 connections.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.18.16 / 6.19.6 or later
Fixed in 6.18.166.19.6
Vendor patch git.kernel.org →
Interim mitigation

Apply the upstream kernel patch which moves socket initialization code to tcp_v6_mapped_child_init() and calls it before ehash insertion to ensure proper socket context is established before the socket becomes visible to other CPUs.

Recommended fix High confidence

Linux Kernel 6.18.16 or 6.19.6 (depending on your current branch)

  1. Verify current kernel version using `uname -r`
  2. Download or obtain the fixed kernel version: 6.18.16 or 6.19.6 (whichever is the latest stable in your kernel branch)
  3. Plan a maintenance window for the kernel upgrade
  4. Back up critical data and ensure system recovery options are available
  5. Install the new kernel package using your distribution's package manager (e.g., `apt-get install linux-image-<version>`, `yum install kernel-<version>`, or equivalent)
  6. Reboot the system to load the new kernel
  7. After reboot, verify the fix is applied by checking `uname -r` shows the fixed version and reviewing the kernel config matches your requirements
Caveat Kernel upgrades may require system reboots and could introduce regressions; test thoroughly in staging before production deployment

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation4.0 h
  • Implementation16.0 h
  • Testing8.0 h
  • Review / QA6.0 h
34.0 hours of engineering $5,960
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $9,536.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-43198 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-43198 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data