GCP-2026-026

<p><strong>Published: </strong>2026-04-30<br/> <strong>Updated: </strong>2026-05-04<br/> <strong>Reference:</strong> <a href="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-31431">CVE-2026-31431</a></p><p><strong>2026-05-04 Update:</strong> Added patch versions for GKE.</p><devsite-selector> <section> <h3 data-text="GKE" id="gcp-2026-026-gke" tabindex="-1">GKE</h3> <p><strong>Updated: </strong>2026-05-04</p> <table> <thead> <tr> <th>Description</th> <th>Severity</th> </tr> </thead> <tbody> <tr> <td> <p>A vulnerability in the Linux kernel (<a href="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-31431">CVE-2026-31431</a>) allows an unprivileged local attacker to write to the system page cache, potentially leading to local privilege escalation and container escape.</p> <p>GKE Standard and Autopilot clusters are affected.</p> <p>Containers using <a href="https://docs.cloud.google.com/kubernetes-engine/docs/how-to/hardening-your-cluster#gke_sandbox">GKE Sandbox</a> are not impacted.</p> <h4 data-text="What should I do?" id="what-should-i-do_17" tabindex="-1">What should I do?</h4> <p><strong>2026-05-04 Update:</strong> The following versions of GKE are updated with code to fix this vulnerability on Container-Optimized OS. <a href="https://docs.cloud.google.com/kubernetes-engine/docs/how-to/upgrading-a-container-cluster">Upgrade</a> your Container-Optimized OS node pools to the following versions or later:</p> <ul> <li>1.36.0-gke.1555000</li> <li>1.35.3-gke.1943000</li> <li>1.34.7-gke.1292000</li> <li>1.33.11-gke.1132000</li> <li>1.32.13-gke.1446000</li> <li>1.31.14-gke.1846000</li> <li>1.30.14-gke.2439000</li> </ul> <p>If you don't see these versions in the Google Cloud console, then use the <a href="https://docs.cloud.google.com/sdk/gcloud/reference/container/clusters/upgrade"><code dir="ltr" translate="no">gcloud container clusters upgrade</code></a> gcloud CLI command to specify the versions and upgrade your node pools in Standard clusters and your control plane in Autopilot clusters.</p> <hr/> <p>Upstream kernel patches have only recently been released. Those patches are being built into GKE releases and this bulletin will be updated when they are available. In the interim, mitigations are available below.</p> <p>We do not recommend relying on containers as a security boundary, container breakout vulnerabilities are very common. <a href="https://docs.cloud.google.com/kubernetes-engine/docs/how-to/hardening-your-cluster#gke_sandbox">Use GKE Sandbox instead</a>.</p> <p>For immediate protection, <a href="https://github.com/GoogleCloudPlatform/k8s-node-tools/tree/master/disable-algif-aead">mitigation advice here</a>.</p> <h4 data-text="What vulnerabilities are being addressed?" id="what-vulnerabilities-are-being-addressed" tabindex="-1">What vulnerabilities are being addressed?</h4> <p>The vulnerability, CVE-2026-31431, is a logic flaw in the Linux kernel's <code dir="ltr" translate="no">authencesn</code> cryptographic template that chains <code dir="ltr" translate="no">AF_ALG</code> and <code dir="ltr" translate="no">splice()</code>. It allows an unprivileged local user to trigger a deterministic, controlled 4-byte write into the page cache of any readable file on the system. Because the page cache is shared across the host, an attacker can exploit this to achieve root privileges or escape container boundaries by corrupting the in-memory versions of setuid binaries or other sensitive files.</p> </td> <td>High</td> </tr> </tbody> </table> </section> <section> <h3 data-text="GDC (VMware)" id="gcp-2026-026-gdcvmware" tabindex="-1">GDC (VMware)</h3> <table> <thead> <tr> <th>Description</th> <th>Severity</th> </tr> </thead> <tbody> <tr> <td> <p>A vulnerability in the Linux kernel (<a href="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-31431">CVE-2026-31431</a>) allows an unprivileged local attacker to write to the system page cache, potentially leading to local privilege escalation and container escape.</p> <h4 data-text="What should I do?" id="what-should-i-do_18" tabindex="-1">What should I do?</h4> <p>Upstream kernel patches have only recently been released. Those patches are being built into GKE releases and this bulletin will be updated when they are available. In the interim, mitigations are available below.</p> <p>We do not recommend relying on containers as a security boundary, container breakout vulnerabilities are very common. <a href="https://docs.cloud.google.com/kubernetes-engine/docs/how-to/hardening-your-cluster#gke_sandbox">Use GKE Sandbox instead</a>.</p> <p>For immediate protection, <a href="https://github.com/GoogleCloudPlatform/k8s-node-tools/tree/master/disable-algif-aead">mitigation advice here</a>.</p> <h4 data-text="What vulnerabilities are being addressed?" id="what-vulnerabilities-are-being-addressed_1" tabindex="-1">What vulnerabilities are being addressed?</h4> <p>The vulnerability, CVE-2026-31431, is a logic flaw in the Linux kernel's <code dir="ltr" translate="no">authencesn</code> cryptographic template that chains <code dir="ltr" translate="no">AF_ALG</code> and <code dir="ltr" translate="no">splice()</code>. It allows an unprivileged local user to trigger a deterministic, controlled 4-byte write into the page cache of any readable file on the system. Because the page cache is shared across the host, an attacker can exploit this to achieve root privileges or escape container boundaries by corrupting the in-memory versions of sensitive files.</p> </td> <td>High</td> </tr> </tbody> </table> </section> <section> <h3 data-text="GKE on AWS" id="gcp-2026-026-gkeaws" tabindex="-1">GKE on AWS</h3> <table> <thead> <tr> <th>Description</th> <th>Severity</th> </tr> </thead> <tbody> <tr> <td> <p>A vulnerability in the Linux kernel (<a href="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-31431">CVE-2026-31431</a>) allows an unprivileged local attacker to write to the system page cache, potentially leading to local privilege escalation and container escape.</p> <h4 data-text="What should I do?" id="what-should-i-do_19" tabindex="-1">What should I do?</h4> <p>Upstream kernel patches have only recently been released. Those patches are being built into GKE releases and this bulletin will be updated when they are available. In the interim, mitigations are available below.</p> <p>We do not recommend relying on containers as a security boundary, container breakout vulnerabilities are very common. <a href="https://docs.cloud.google.com/kubernetes-engine/docs/how-to/hardening-your-cluster#gke_sandbox">Use GKE Sandbox instead</a>.</p> <p>For immediate protection, <a href="https://github.com/GoogleCloudPlatform/k8s-node-tools/tree/master/disable-algif-aead">mitigation advice here</a>.</p> <h4 data-text="What vulnerabilities are being addressed?" id="what-vulnerabilities-are-being-addressed_2" tabindex="-1">What vulnerabilities are being addressed?</h4> <p>The vulnerability, CVE-2026-31431, is a logic flaw in the Linux kernel's <code dir="ltr" translate="no">authencesn</code> cryptographic template that chains <code dir="ltr" translate="no">AF_ALG</code> and <code dir="ltr" translate="no">splice()</code>. It allows an unprivileged local user to trigger a deterministic, controlled 4-byte write into the page cache of any readable file on the system. Because the page cache is shared across the host, an attacker can exploit this to achieve root privileges or escape container boundaries by corrupting the in-memory versions of sensitive files.</p> </td> <td>High</td> </tr> </tbody> </table> </section> <section> <h3 data-text="GKE on Azure" id="gcp-2026-026-gkeazure" tabindex="-1">GKE on Azure</h3> <table> <thead> <tr> <th>Description</th> <th>Severity</th> </tr> </thead> <tbody> <tr> <td> <p>A vulnerability in the Linux kernel (<a href="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-31431">CVE-2026-31431</a>) allows an unprivileged local attacker to write to the system page cache, potentially leading to local privilege escalation and container escape.</p> <h4 data-text="What should I do?" id="what-should-i-do_20" tabindex="-1">What should I do?</h4> <p>Upstream kernel patches have only recently been released. Those patches are being built into GKE releases and this bulletin will be updated when they are available. In the interim, mitigations are available below.</p> <p>We do not recommend relying on containers as a security boundary, container breakout vulnerabilities are very common. <a href="https://docs.cloud.google.com/kubernetes-engine/docs/how-to/hardening-your-cluster#gke_sandbox">Use GKE Sandbox instead</a>.</p> <p>For immediate protection, <a href="https://github.com/GoogleCloudPlatform/k8s-node-tools/tree/master/disable-algif-aead">mitigation advice here</a>.</p> <h4 data-text="What vulnerabilities are being addressed?" id="what-vulnerabilities-are-being-addressed_3" tabindex="-1">What vulnerabilities are being addressed?</h4> <p>The vulnerability, CVE-2026-31431, is a logic flaw in the Linux kernel's <code dir="ltr" translate="no">authencesn</code> cryptographic template that chains <code dir="ltr" translate="no">AF_ALG</code> and <code dir="ltr" translate="no">splice()</code>. It allows an unprivileged local user to trigger a deterministic, controlled 4-byte write into the page cache of any readable file on the system. Because the page cache is shared across the host, an attacker can exploit this to achieve root privileges or escape container boundaries by corrupting the in-memory versions of sensitive files.</p> </td> <td>High</td> </tr> </tbody> </table> </section> <section> <h3 data-text="GDC (bare metal)" id="gcp-2026-026-gdcbm" tabindex="-1">GDC (bare metal)</h3> <table> <thead> <tr> <th>Description</th> <th>Severity</th> </tr> </thead> <tbody> <tr> <td> <p>A vulnerability in the Linux kernel (<a href="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-31431">CVE-2026-31431</a>) allows an unprivileged local attacker to write to the system page cache, potentially leading to local privilege escalation and container escape.</p> <h4 data-text="What should I do?" id="what-should-i-do_21" tabindex="-1">What should I do?</h4> <p>GDC software for bare metal does not bundle an operating system in its distribution. Customers are responsible for installing and maintaining a supported Linux distribution on physical hardware.</p> <p>To protect your cluster, check with your OS vendor to see if your underlying Linux distribution is affected, and apply the appropriate kernel updates.</p> <p>As an immediate mitigation, <a href="https://github.com/GoogleCloudPlatform/k8s-node-tools/tree/master/disable-algif-aead">mitigation advice here</a>.</p> <h4 data-text="What vulnerabilities are being addressed?" id="what-vulnerabilities-are-being-addressed_4" tabindex="-1">What vulnerabilities are being addressed?</h4> <p>The vulnerability, CVE-2026-31431, is a logic flaw in the Linux kernel's <code dir="ltr" translate="no">authencesn</code> cryptographic template that chains <code dir="ltr" translate="no">AF_ALG</code> and <code dir="ltr" translate="no">splice()</code>. It allows an unprivileged local user to trigger a deterministic, controlled 4-byte write into the page cache of any readable file on the system. Because the page cache is shared across the host, an attacker can exploit this to achieve root privileges or escape container boundaries by corrupting the in-memory versions of sensitive files.</p> </td> <td>High</td> </tr> </tbody> </table> </section> </devsite-selector>