CVE-2026-31470: 
Linux Kernel vulnerability analysis and mitigation

CVE-2026-31470 is a buffer over-read vulnerability in the Linux kernel's TDX (Trust Domain Extensions) guest driver that fails to properly validate a host-controlled quote buffer length (quote_buf->out_len). This flaw allows a malicious or compromised host to specify a response length larger than the guest's allocated buffer, or to race-condition modify the response while the guest consumes it, potentially leaking memory contents beyond the intended allocation. Affected Linux kernel versions span from 6.7 up to (but not including) 6.12.80, 6.13 up to 6.18.21, 6.19 up to 6.19.11, and pre-release 7.0 release candidates. It was published on April 22, 2026, with patches available the same day. The vulnerability carries a CVSS v3.1 base score of 7.1 (High) (GitHub Advisory, Red Hat Bugzilla).

The root cause is insufficient validation of the host-controlled value quote_buf->out_len in the virt/tdx-guest kernel subsystem, classified as CWE-125 (Out-of-bounds Read) and CWE-787 (Out-of-bounds Write). In TDX environments, the host can supply a out_len value exceeding the guest's allocated buffer pages, causing the kernel to copy memory contents beyond the quote_buf allocation (up to TSM_REPORT_OUTBLOB_MAX) into guest userspace. A race condition is also possible, where the host modifies the response buffer while the guest is actively consuming it, further enabling unintended memory disclosure. The attack requires local access with low privileges (e.g., a container or guest process) in a TDX-enabled virtualization environment with remote attestation configured (GitHub Advisory, Red Hat Bugzilla).

Successful exploitation can result in high confidentiality impact — sensitive memory contents beyond the intended quote buffer may be read out to guest userspace and potentially forwarded to remote attestation servers, exposing data that crosses container protection boundaries in per-container configs-tsm-report deployments. Availability is also rated high, as the race condition or malformed length could destabilize the guest's attestation flow. There is no integrity impact, but the cross-container data leakage risk is particularly significant in multi-tenant cloud environments using TDX-based confidential computing (GitHub Advisory, Feedly).

There is no public proof-of-concept exploit and no evidence of in-the-wild exploitation as of the time of this report (Feedly). The EPSS score is approximately 0.018% (3rd percentile), indicating a very low near-term exploitation probability (GitHub Advisory). The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. Exploitation requires local access with low privileges in a TDX-enabled environment, limiting the attack surface to specialized confidential computing deployments.

Apply the available Linux kernel patches that address this vulnerability: upgrade to kernel version 6.12.80 or later (for the 6.12 stable branch), 6.18.21 or later (for the 6.13–6.18 range), 6.19.11 or later (for the 6.19 branch), or the 7.0 stable release. Patch commits are available at the upstream kernel stable tree (kernel.org patches). Vendor-specific updates have been issued by Red Hat, SUSE (SUSE-SU-2026:2195-1, SUSE-SU-2026:2215-1, SUSE-SU-2026:2238-1), Amazon Linux 2023, and openSUSE. Organizations running TDX-based confidential computing workloads with remote attestation should prioritize patching immediately and audit any attestation data previously collected from vulnerable systems (Red Hat Bugzilla, GitHub Advisory).

Red Hat tracked this vulnerability via Bugzilla (BZ#2460674) and assigned a CVSS v3.1 score of 7.1. SUSE issued multiple security advisories (SUSE-SU-2026:2195-1, SUSE-SU-2026:2215-1, SUSE-SU-2026:2238-1) addressing the flaw across their kernel packages. Amazon Linux 2023 also released advisories (ALAS2023-2026-1646 and ALAS2023-2026-1746). The Yocto Project security mailing list flagged the issue for embedded Linux maintainers. No notable independent researcher commentary or significant social media discussion has been identified beyond standard vendor patch tracking (Red Hat Bugzilla).