CVE-2021-38187Network attack vector

Undefined behavior via unaligned TypeIdHasher pointer cast

Published Aug 8, 2021 · Updated Aug 4, 2024

Soundness violation in the anymap crate 0.12.1 and earlier allows attackers to trigger undefined behavior during type hashing. TypeIdHasher::write in src/raw.rs casts a byte-slice pointer from *const u8 to the more strictly aligned *const u64 and copies through it without ensuring eight-byte alignment. The path is reached when a consuming Rust program hashes type identifiers through the affected map, and an unaligned access produces undefined behavior.

CVSS severity9.8
Critical
EPSS probability1.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Soundness violation in the anymap crate 0.12.1 and earlier allows attackers to trigger undefined behavior during type hashing. TypeIdHasher::write in src/raw.rs casts a byte-slice pointer from *const u8 to the more strictly aligned *const u64 and copies through it without ensuring eight-byte alignment. The path is reached when a consuming Rust program hashes type identifiers through the affected map, and an unaligned access produces undefined behavior.

The record

CVE
CVE-2021-38187
Published
Aug 8, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-704, CWE-681
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 8, 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 vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-704Incorrect Type Conversion or Cast
CWE-681Incorrect Conversion between Numeric Types

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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