# Time-of-check time-of-use race condition in AMD Ryzen™ 3000 Series Desktop Processors “Matisse” AM4 and others

CVE record · `CVE-2021-26356`

- **Identifiers:** `CVE-2021-26356`
- **State:** Confirmed
- **Severity:** CVSS 7.4 High
- **Critical:** No
- **CNA:** AMD
- **Weakness (CWE):** [CWE-367](https://cwe.mitre.org/data/definitions/367.html)
- **Tags:** [Race condition](https://agentprime.io/advisories/tag/race-condition.md)
- **Technologies:** [AMD Ryzen™ 3000 Series Desktop Processors “Matisse” AM4](https://agentprime.io/advisories/technology/amd-ryzentm-3000-series-desktop-processors-matisse-am4.md) · [AMD Ryzen™ 5000 Series Desktop Processors “Vermeer” AM4](https://agentprime.io/advisories/technology/amd-ryzentm-5000-series-desktop-processors-vermeer-am4.md) · [3rd Gen AMD Ryzen™ Threadripper™ Processors “Castle Peak” HEDT](https://agentprime.io/advisories/technology/3rd-gen-amd-ryzentm-threadrippertm-processors-castle-peak-hedt.md) · [AMD Ryzen™ Threadripper™ PRO Processors “Castle Peak” WS](https://agentprime.io/advisories/technology/amd-ryzentm-threadrippertm-pro-processors-castle-peak-ws.md) · [AMD Ryzen™ Threadripper™ PRO Processors “Chagall” WS](https://agentprime.io/advisories/technology/amd-ryzentm-threadrippertm-pro-processors-chagall-ws.md) · [1st Gen AMD EPYC™ Processors](https://agentprime.io/advisories/technology/1st-gen-amd-epyctm-processors.md) · [2nd Gen AMD EPYC™ Processors](https://agentprime.io/advisories/technology/2nd-gen-amd-epyctm-processors.md) · [3rd Gen AMD EPYC™ Processors](https://agentprime.io/advisories/technology/3rd-gen-amd-epyctm-processors.md)
- **Published:** 9 May 2023
- **Updated:** 28 Jan 2025
- **Reviewed by a person:** No

Published by the CVE Program (CNA: AMD) at 9 May 2023, 18:58 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

## Affected products, as the CNA wrote them

- Vendor: AMD. Product: Ryzen™ 3000 Series Desktop Processors “Matisse” AM4.
  - affected: `various`
  - Other versions: unaffected
  - Package name: `AGESA`
- Vendor: AMD. Product: AMD Ryzen™ 5000 Series Desktop Processors “Vermeer” AM4.
  - affected: `various`
  - Other versions: unaffected
  - Package name: `AGESA`
- Vendor: AMD. Product: 3rd Gen AMD Ryzen™ Threadripper™ Processors “Castle Peak” HEDT.
  - affected: `various`
  - Other versions: unaffected
  - Package name: `AGESA`
- Vendor: AMD. Product: Ryzen™ Threadripper™ PRO Processors “Castle Peak” WS.
  - affected: `various`
  - Other versions: unaffected
  - Package name: `AGESA`
- Vendor: AMD. Product: Ryzen™ Threadripper™ PRO Processors “Chagall” WS.
  - affected: `various`
  - Other versions: unaffected
  - Package name: `AGESA`
- Vendor: AMD. Product: 1st Gen AMD EPYC™ Processors.
  - affected: `various`
  - Other versions: unaffected
  - Package name: `AGESA`
- Vendor: AMD. Product: 2nd Gen AMD EPYC™ Processors.
  - affected: `various`
  - Other versions: unaffected
  - Package name: `AGESA`
- Vendor: AMD. Product: 3rd Gen AMD EPYC™ Processors.
  - affected: `various`
  - Other versions: unaffected
  - Package name: `AGESA`

## Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

## Severity and exploitation

- 7.4 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N`, from ADP (CISA-ADP)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0040, the 34th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the CVE Program, published 9 May 2023. New records show when each source confirmed them.

## Sources

- [CVE List: CVE-2021-26356](https://www.cve.org/CVERecord?id=CVE-2021-26356)
- [NVD: CVE-2021-26356](https://nvd.nist.gov/vuln/detail/CVE-2021-26356)

### References from the CNA

- <https://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-4001> (vendor-advisory)
- <https://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-3001> (vendor-advisory)

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.

## Check whether this affects you

This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it. Compare the affected versions above with what you run.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), `get_advisory` returns this record and `search_advisories` finds related ones. Setup: <https://agentprime.io/mcp.md>
- As JSON: <https://api.agentprime.io/v1/advisories/CVE-2021-26356>
- Everything that needs attention now: <https://agentprime.io/advisories/critical.md>

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The web page: <https://agentprime.io/advisories/CVE-2021-26356/>. Everything for agents: <https://agentprime.io/llms.txt>.