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Linux KernelOperating system · Linux

CVE-2026-53228

CRITICAL · 9.8 CVSS v3.1 Published 2026-06-25
Fix available
A fix is available. Upgrade to 5.10.259 / 5.15.210 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: ipv6: sit: reload inner IPv6 header after GSO offloads ipip6_tunnel_xmit() caches the inner IPv6 header pointer at function entry and continues using it after iptunnel_handle_offloads(). For GSO skbs, iptunnel_handle_offloads() calls skb_header_unclone(). When the skb header is cloned, skb_header_unclone() can call pskb_expand_head(), which may move the skb head. The pskb_expand_head() contract requires pointers into the skb header to be reloaded after the call. If the later skb_realloc_headroom() branch is not taken, SIT uses the stale iph6 pointer to read the inner hop limit and DS field. That can read from a freed skb head after the old head's remaining clone is released. Reload iph6 after the offload helper succeeds and before subsequent reads from the inner IPv6 header. Keep the existing reload after skb_realloc_headroom(), since that branch can also replace the skb.

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

Use-after-free vulnerability in Linux kernel's IPv6 SIT tunnel driver where ipip6_tunnel_xmit() caches the inner IPv6 header pointer at function entry but continues using it after iptunnel_handle_offloads() calls skb_header_unclone(), which can invoke pskb_expand_head() and move the skb head, causing the stale pointer to read from freed memory when accessing inner hop limit and DS field.

MitigationApply the kernel patch to reload the inner IPv6 header pointer after iptunnel_handle_offloads() succeeds; this is a kernel-level fix requiring kernel update deployment.

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:>= 3.18, < 5.10.259>= 5.11, < 5.15.210>= 5.16, < 6.1.176>= 6.2, < 6.6.143>= 6.7, < 6.12.94>= 6.13, < 6.18.36>= 6.19, < 7.0.13= 7.1

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 the running kernel version
    Run `uname -r` or `cat /proc/version` to obtain the kernel version string
    Affected if The version falls within any of these ranges: >= 3.18 and < 5.10.259; >= 5.11 and < 5.15.210; >= 5.16 and < 6.1.176; >= 6.2 and < 6.6.143; >= 6.7 and < 6.12.94; >= 6.13 and < 6.18.36; >= 6.19 and < 7.0.13; or equals 7.1
  2. Verify if IPv6 SIT tunnels are configured
    Run `ip -6 tunnel show` or check for active tunnel interfaces with `ip link show` that use the 'sit' tunnel mode
    Affected if Any IPv6 SIT tunnel interfaces exist on the system (e.g., sit0, or custom sit tunnels)
  3. Confirm if tunnel is carrying traffic
    Monitor the tunnel interface with `ip -s link show <tunnel-name>` or check tunnel statistics in `/proc/net/dev`
    Affected if The SIT tunnel interface shows non-zero packet counters indicating active traffic flow

A system is affected if it runs a kernel version within the affected ranges AND has an active IPv6 SIT tunnel carrying traffic that triggers the GSO path in ipip6_tunnel_xmit().

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 5.10.259 / 5.15.210 / 6.1.176 or later
Fixed in 5.10.2595.15.2106.1.176
Vendor patch git.kernel.org →
Interim mitigation

Apply the kernel patch to reload the inner IPv6 header pointer after iptunnel_handle_offloads() succeeds; this is a kernel-level fix requiring kernel update deployment.

Recommended fix High confidence

Upgrade to kernel >= 5.10.259, >= 5.15.210, >= 6.1.176, or >= 6.6.143 depending on your current branch

  1. Identify the currently running kernel version using `uname -r`
  2. Determine which version range your current kernel falls into (5.10.x, 5.15.x, 6.1.x, or 6.2-6.6.x)
  3. Obtain a kernel upgrade to a version >= the first fixed version for your branch: 5.10.259, 5.15.210, 6.1.176, or 6.6.143 respectively
  4. Apply the kernel upgrade via your distribution's package manager (e.g., `apt-get dist-upgrade`, `yum update`, or `dnf upgrade`)
  5. Reboot the system to load the patched kernel
  6. Verify the running kernel version with `uname -r` and confirm it matches a fixed release
Caveat Kernel upgrades may require rebooting services and could introduce compatibility changes with custom kernel modules or older system utilities

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

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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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-2026-53228 in production — separate from our analysis above.

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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