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Linux KernelOperating system · Linux

CVE-2026-31633

CRITICAL · 9.8 CVSS v3.1 Published 2026-04-24
Fix available
A fix is available. Upgrade to 6.18.23 / 6.19.13 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: rxrpc: Fix integer overflow in rxgk_verify_response() In rxgk_verify_response(), there's a potential integer overflow due to rounding up token_len before checking it, thereby allowing the length check to be bypassed. Fix this by checking the unrounded value against len too (len is limited as the response must fit in a single UDP packet).

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 · moderate confidence

Integer overflow in rxgk_verify_response() in the Linux kernel's rxrpc protocol implementation allows bypassing length checks due to rounding up token_len before validation. This enables an attacker to craft malicious UDP packets that bypass the length check, potentially leading to buffer overflow or memory corruption.

MitigationApply the kernel patch that adds validation of the unrounded token_len value against the response length before performing the rounding operation. Since the response must fit in a single UDP packet, ensure kernel versions are updated to include this fix.

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:>= 6.16.1, < 6.18.23>= 6.19, < 6.19.13= 6.16= 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 your kernel version
    Run 'uname -r' to get the running kernel version, then compare it against the affected ranges: >= 6.16.1, < 6.18.23; >= 6.19, < 6.19.13; = 6.16; = 7.0
    Affected if The kernel version matches any of the listed affected versions
  2. Verify the rxrpc kernel module is loaded
    Run 'lsmod | grep rxrpc' or check /proc/modules to see if the rxrpc module is currently loaded in memory
    Affected if The rxrpc module is loaded and the kernel version is in the affected range
  3. Confirm rxgk functionality is present
    Run 'lsmod | grep rxgk' to check if the rxgk module (RxRPC GSSAPI) is loaded, which provides the rxgk_verify_response() function containing the flaw
    Affected if The rxgk module is loaded and the kernel version is in the affected range
  4. Check if kernel was built with rxrpc support
    If the modules are not loaded, check the kernel configuration file (usually /boot/config-$(uname -r) or /proc/config.gz) for CONFIG_RXRPC=y or CONFIG_RXRPC=m
    Affected if RxRPC support is compiled into the kernel and the kernel version is in the affected range

You are affected if your running kernel version falls within any of the affected ranges AND the rxrpc subsystem with rxgk is present in your environment.

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 6.18.23 / 6.19.13 or later
Fixed in 6.18.236.19.13
Vendor patch git.kernel.org →
Interim mitigation

Apply the kernel patch that adds validation of the unrounded token_len value against the response length before performing the rounding operation. Since the response must fit in a single UDP packet, ensure kernel versions are updated to include this fix.

Recommended fix High confidence

Linux Kernel 6.18.23 or later, or 6.19.13 or later (or the next stable release after these versions)

  1. Identify the current kernel version using `uname -r`
  2. Check if the running kernel version is affected: >= 6.16.1 and < 6.18.23, or >= 6.19 and < 6.19.13, or exactly 6.16 or 7.0
  3. Plan a kernel upgrade to a fixed version (6.18.23+, 6.19.13+, or later stable release)
  4. Backup critical data before kernel upgrade
  5. Upgrade the kernel using your distribution's package manager (e.g., `apt-get dist-upgrade`, `yum update`, or equivalent)
  6. Reboot the system to load the patched kernel
  7. Verify the new kernel version is running with `uname -r` and confirm it is a fixed version
Caveat Kernel upgrades may require rebooting services; some driver or module incompatibilities could occur if using third-party kernel modules

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
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,920
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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-2026-31633 in production — separate from our analysis above.

No notes yet

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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