dbcve.org
Linux KernelOperating system · Linux

CVE-2026-43038

CRITICAL · 9.8 CVSS v3.1 Published 2026-05-01
Fix available
A fix is available. Upgrade to 5.10.253 / 5.15.203 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: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach() Sashiko AI-review observed: In ip6_err_gen_icmpv6_unreach(), the skb is an outer IPv4 ICMP error packet where its cb contains an IPv4 inet_skb_parm. When skb is cloned into skb2 and passed to icmp6_send(), it uses IP6CB(skb2). IP6CB interprets the IPv4 inet_skb_parm as an inet6_skb_parm. The cipso offset in inet_skb_parm.opt directly overlaps with dsthao in inet6_skb_parm at offset 18. If an attacker sends a forged ICMPv4 error with a CIPSO IP option, dsthao would be a non-zero offset. Inside icmp6_send(), mip6_addr_swap() is called and uses ipv6_find_tlv(skb, opt->dsthao, IPV6_TLV_HAO). This would scan the inner, attacker-controlled IPv6 packet starting at that offset, potentially returning a fake TLV without checking if the remaining packet length can hold the full 18-byte struct ipv6_destopt_hao. Could mip6_addr_swap() then perform a 16-byte swap that extends past the end of the packet data into skb_shared_info? Should the cb array also be cleared in ip6_err_gen_icmpv6_unreach() and ip6ip6_err() to prevent this? This patch implements the first suggestion. I am not sure if ip6ip6_err() needs to be changed. A separate patch would be better anyway.

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

In the Linux kernel's ip6_err_gen_icmpv6_unreach() function, an IPv4 ICMP error packet's control buffer (cb) containing inet_skb_parm is incorrectly interpreted as inet6_skb_parm when passed to icmp6_send(). The cipso offset overlaps with dsthao at offset 18, allowing an attacker to trigger mip6_addr_swap() with a manipulated offset into attacker-controlled IPv6 packet data, potentially causing out-of-bounds read/write beyond packet boundaries.

MitigationApply the kernel patch to clear skb2->cb[] in ip6_err_gen_icmpv6_unreach(). Until patched, restrict ICMPv4 error processing at network perimeter or disable IPv6 if not required.

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:> 3.13, < 5.10.253>= 5.11, < 5.15.203>= 5.16, < 6.1.168>= 6.2, < 6.6.134>= 6.7, < 6.12.81>= 6.13, < 6.18.22>= 6.19, < 6.19.12= 3.13= 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 kernel version against affected ranges
    Run 'uname -r' or read /proc/version to get the installed kernel version
    Affected if The kernel version falls within any of these ranges: >3.13 and <5.10.253; >=5.11 and <5.15.203; >=5.16 and <6.1.168; >=6.2 and <6.6.134; >=6.7 and <6.12.81; >=6.13 and <6.18.22; >=6.19 and <6.19.12; or equals 3.13 or 7.0
  2. Verify IPv6 kernel module is loaded or compiled in
    Check if IPv6 is enabled by examining 'lsmod | grep ipv6' or checking /proc/sys/net/ipv6/conf/all/disable
    Affected if IPv6 is enabled (not disabled) and the kernel version is in the affected list above
  3. Confirm system processes ICMP traffic
    Monitor for incoming ICMP packets using 'tcpdump -i any icmp' or check existing network traffic logs
    Affected if The system receives IPv4 ICMP error packets containing CIPSO IP options from untrusted network sources

A system is affected if it runs a vulnerable kernel version (as listed above), has IPv6 enabled, and can receive IPv4 ICMP error packets with CIPSO options from potentially malicious sources.

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 5.10.253 / 5.15.203 / 6.1.168 or later
Fixed in 5.10.2535.15.2036.1.168
Vendor patch git.kernel.org →
Interim mitigation

Apply the kernel patch to clear skb2->cb[] in ip6_err_gen_icmpv6_unreach(). Until patched, restrict ICMPv4 error processing at network perimeter or disable IPv6 if not required.

Recommended fix High confidence

Linux Kernel 6.1.168 (or 5.10.253/5.15.203/6.6.134 depending on your branch)

  1. 1. Identify the currently running Linux kernel version using `uname -r`
  2. 2. Determine which branch of the kernel you are running (e.g., 5.10.x, 5.15.x, 6.1.x, or 6.6.x)
  3. 3. Upgrade to a kernel version that includes the fix: 5.10.253 or later for 5.10.y, 5.15.203 or later for 5.15.y, 6.1.168 or later for 6.1.y, or 6.6.134 or later for 6.6.y
  4. 4. Apply the upgrade via your distribution's package manager (e.g., `apt-get update && apt-get upgrade`, `yum update`, or `dnf upgrade`)
  5. 5. Reboot the system to load the new kernel
  6. 6. Verify the new kernel version is running with `uname -r`
Caveat Kernel upgrades may require reboot and could introduce compatibility issues with proprietary kernel modules or older drivers; ensure critical modules are compatible 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
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing8.0 h
  • Review / QA3.0 h
20.0 hours of engineering $3,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,472.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-43038 — 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-2026-43038 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