CVE-2021-26313Public exploit

Data leakage via transient stale-code execution

Published Jun 9, 2021 · Updated Sep 16, 2024

Speculative code store bypass in AMD CPU products allows local users to leak data through transient execution of stale instructions. A delayed self-modifying-code machine clear leaves instruction and data views inconsistent, causing the processor to decode and transiently execute overwritten code from a stale instruction stream. Exploitation requires software that overwrites executable instructions without effective serialization; researchers found candidate gadgets in real-world code, but none were ultimately exploitable.

CVSS severity5.5
Medium
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Speculative code store bypass in AMD CPU products allows local users to leak data through transient execution of stale instructions. A delayed self-modifying-code machine clear leaves instruction and data views inconsistent, causing the processor to decode and transiently execute overwritten code from a stale instruction stream. Exploitation requires software that overwrites executable instructions without effective serialization; researchers found candidate gadgets in real-world code, but none were ultimately exploitable.

The record

CVE
CVE-2021-26313
Published
Jun 9, 2021
Updated
Sep 16, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-203, CWE-208, T1005
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
2.1NIST NVDAV:L/AC:L/Au:N/C:P/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-203Observable Discrepancy
CWE-208Observable Timing Discrepancy
T1005Data from Local System

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo