CVE-2026-31470
Published: 22 April 2026
Summary
CVE-2026-31470 is a high-severity Out-of-bounds Write (CWE-787) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.1 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Data from Local System (T1005); ranked at the 2.4th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly mitigates the CVE by requiring timely patching of the Linux kernel TDX guest flaw with validation of host-controlled quote buffer length.
Enforces validation of the untrusted host-provided `quote_buf->out_len` to prevent out-of-bounds copies to guest userspace and memory leaks.
Provides memory protections that mitigate unauthorized disclosure of guest memory contents beyond allocated quote buffer pages.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Out-of-bounds read in TDX guest kernel directly enables local memory content leakage (T1005 Data from Local System) across containers and can trigger crashes/DoS (T1499 Endpoint Denial of Service).
NVD Description
In the Linux kernel, the following vulnerability has been resolved: virt: tdx-guest: Fix handling of host controlled 'quote' buffer length Validate host controlled value `quote_buf->out_len` that determines how many bytes of the quote are copied out to guest userspace. In…
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TDX environments with remote attestation, quotes are not considered private, and can be forwarded to an attestation server. Catch scenarios where the host specifies a response length larger than the guest's allocation, or otherwise races modifying the response while the guest consumes it. This prevents contents beyond the pages allocated for `quote_buf` (up to TSM_REPORT_OUTBLOB_MAX) from being read out to guest userspace, and possibly forwarded in attestation requests. Recall that some deployments want per-container configs-tsm-report interfaces, so the leak may cross container protection boundaries, not just local root.
Deeper analysisAI
CVE-2026-31470 is a vulnerability in the Linux kernel's TDX guest module, which handles Intel Trust Domain Extensions (TDX) environments for confidential computing and remote attestation. The issue stems from improper validation of the host-controlled `quote_buf->out_len` value, which dictates the number of bytes copied from the attestation quote buffer to guest userspace. Without proper checks, this allows the guest to copy data beyond its allocated pages—up to the TSM_REPORT_OUTBLOB_MAX limit—potentially exposing unintended memory contents. Quotes in TDX are not private and can be forwarded to attestation servers.
A local attacker with low privileges (PR:L) on the affected TDX guest system can exploit this vulnerability with low complexity (AC:L) and no user interaction (UI:N). By triggering quote generation or consumption via interfaces like per-container configs-tsm-report, the attacker can cause the guest to read out-of-bounds data based on a maliciously large `quote_buf->out_len` set by the host, or exploit races during response modification. This results in high confidentiality impact (C:H) through memory leaks that may cross container boundaries, and high availability impact (A:H) from potential crashes or denial of service, all within the guest's unchanged scope (S:U).
Mitigation requires applying kernel patches from the referenced stable commits, including 02ca2d9d197723696cb9cc0cb159eb7e8bf5f89b, 6f3c8795ae9ba74fa10fe979293d1904712d3fb1, a079a62883e3365de592cea9f7a669d8115433b0, and c3fd16c3b98ed726294feab2f94f876290bf7b61. These fixes add validation for the host-controlled length and handle races, preventing excessive copies to userspace. Security practitioners should update TDX guest kernels promptly, especially in multi-tenant or containerized deployments.
Details
- CWE(s)