CVE-2023-40271Network attack vector

Payload authentication bypass via four-byte tag comparison

Published Sep 8, 2023 · Updated Sep 26, 2024

Incorrect tag verification in Trusted Firmware-M 1.6.0 through 1.8.0 allows attackers to pass unauthenticated payloads as authentic via network input. In cc3xx_decrypt_chacha20_poly1305(), the comparison loop uses sizeof(tag_length), checking four bytes rather than the full 16-byte tag length. Reachability requires a CC312-enabled build with the legacy driver disabled and the dedicated single-part ChaCha20-Poly1305 path enabled.

CVSS severity7.5
High
EPSS probability0.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect tag verification in Trusted Firmware-M 1.6.0 through 1.8.0 allows attackers to pass unauthenticated payloads as authentic via network input. In cc3xx_decrypt_chacha20_poly1305(), the comparison loop uses sizeof(tag_length), checking four bytes rather than the full 16-byte tag length. Reachability requires a CC312-enabled build with the legacy driver disabled and the dedicated single-part ChaCha20-Poly1305 path enabled.

The record

CVE
CVE-2023-40271
Published
Sep 8, 2023
Updated
Sep 26, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-697
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 8, 2023CVE publishedPublication date reported by the CVE source.
  2. Sep 26, 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

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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.

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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-697Incorrect Comparison

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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