# CVE-2026-40669: AMD Secure Encrypted Virtualization off-by-one error in firmware

Source: https://junglewise.ai/threats/cve-2026-40669-an-off-by-one-error-in-amd-secure-encrypted-virtualization-sev  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-10. Updated: 2026-11-10  
License: CC BY 4.0 with a link back

CVE-2026-40669 · Severity: info · Published 2026-11-10

AMD's Secure Encrypted Virtualization (SEV) firmware contains an off-by-one error that could allow a hypervisor administrator to corrupt the Reverse Map Table, which protects guest virtual machine memory integrity. An attacker exploiting this flaw could undermine the confidentiality and integrity guarantees that SEV provides to guest workloads running on shared infrastructure.

Technologies: [Amd Secure Encrypted Virtualization (SEV) firmware](https://junglewise.ai/threats/technologies/secure-encrypted-virtualization-sev-firmware). Vendors: [Amd](https://junglewise.ai/threats/vendors/amd).

## Quick answers

**Is CVE-2026-40669 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-40669 being exploited in the wild.

**How severe is CVE-2026-40669?** Informational severity, published 10 November 2026.

**Which products and versions are affected?** AMD Secure Encrypted Virtualization (SEV) firmware.

**Is there a fix for CVE-2026-40669?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-40669 attacked?** It is attacked from the adjacent network, in device firmware.

**Am I affected by CVE-2026-40669?** Check whether you run Amd Secure Encrypted Virtualization (SEV) firmware. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An off-by-one error in the SEV firmware's Reverse Map Table (RMP) handling allows an attacker with hypervisor-level access to trigger memory corruption in the RMP structure. This vulnerability requires prior compromise of the hypervisor and direct access to SEV firmware interfaces. Exploitation could result in loss of guest memory integrity protections in virtualized environments.

## Affected products

- AMD Secure Encrypted Virtualization (SEV) firmware

## Timeline

- 2026-11-10: disclosed

## References

- [https://www.amd.com/en/resources/product-security/bulletin/AMD-SB-3038.html](https://www.amd.com/en/resources/product-security/bulletin/AMD-SB-3038.html)

## Related threats

- [AMD Secure Encrypted Virtualization firmware use-after-free](https://junglewise.ai/threats/cve-2026-0435-operation-on-a-resource-after-expiration-or-release-in-the-amd)
- [AMD SEV firmware downgrade in ASP Bootloader](https://junglewise.ai/threats/cve-2026-0003-use-of-a-per-part-static-key-in-the-asp-bootloader-could-allow-an)
- [AMD Secure Encrypted Virtualization SEV firmware integrity weakness](https://junglewise.ai/threats/cve-2026-28248-improper-enforcement-of-behavioral-workflow-in-amd-secure)
- [AMD SEV firmware access control bypass in trusted region](https://junglewise.ai/threats/cve-2025-54504-insufficient-granularity-of-access-control-in-amd-secure)