CVE-2021-45696Public exploit

Incorrect hashes via misloaded AVX2 data lane

Published Dec 26, 2021 · Updated Aug 4, 2024

Cryptographic failure in RustCrypto sha2 0.9.7 allows context-dependent attackers to cause incorrect hashes for long messages. The load_data_avx2 routine inserts the second 128-bit lane from data offset i+1 instead of offset 8+i when compressing two SHA-512 blocks in parallel. Exposure requires an x86 or x86_64 CPU with AVX2 autodetected at runtime and a message of at least 256 bytes containing two different blocks.

CVSS severity9.8
Critical
EPSS probability0.80%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cryptographic failure in RustCrypto sha2 0.9.7 allows context-dependent attackers to cause incorrect hashes for long messages. The load_data_avx2 routine inserts the second 128-bit lane from data offset i+1 instead of offset 8+i when compressing two SHA-512 blocks in parallel. Exposure requires an x86 or x86_64 CPU with AVX2 autodetected at runtime and a message of at least 256 bytes containing two different blocks.

The record

CVE
CVE-2021-45696
Published
Dec 26, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-327
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Dec 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-327Use of a Broken or Risky Cryptographic Algorithm

Public exploit references

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Technologies

Your stack

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Your stack

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