CVE-2021-45709

Undefined behavior via unaligned ChaCha20 slices

Published Dec 26, 2021 · Updated Aug 4, 2024

Memory unsoundness in the crypto2 crate allows context-dependent attackers to trigger undefined behavior with unaligned ChaCha20 input slices. The affected slice functions pass a byte-derived pointer to unsafe std::slice::from_raw_parts_mut while incorrectly assuming four-byte u32 alignment. Reachability depends on a consuming application supplying misaligned input; a debug standard-library build panics, while other consequences are unspecified.

CVSS severity9.8
Critical
EPSS probability0.75%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory unsoundness in the crypto2 crate allows context-dependent attackers to trigger undefined behavior with unaligned ChaCha20 input slices. The affected slice functions pass a byte-derived pointer to unsafe std::slice::from_raw_parts_mut while incorrectly assuming four-byte u32 alignment. Reachability depends on a consuming application supplying misaligned input; a debug standard-library build panics, while other consequences are unspecified.

The record

CVE
CVE-2021-45709
Published
Dec 26, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-119, T1499
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 NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS: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.

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)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

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Your stack

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