CVE-2021-37588Public exploitNetwork attack vector

Unauthorized decryption via two-user key collusion

Published Jul 27, 2021 · Updated Aug 4, 2024

Cryptographic weakness in JHUISI Charm 0.43 allows attackers to decrypt YCT14 ciphertexts through two-user collusion. The YCT14 scheme's key algebra permits secret keys for disjoint attribute sets to be combined into decryption material satisfying a ciphertext policy. The attack requires two registered users with complementary attributes and exposes plaintext that neither user is authorized to read alone.

CVSS severity5.9
Medium
EPSS probability0.91%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cryptographic weakness in JHUISI Charm 0.43 allows attackers to decrypt YCT14 ciphertexts through two-user collusion. The YCT14 scheme's key algebra permits secret keys for disjoint attribute sets to be combined into decryption material satisfying a ciphertext policy. The attack requires two registered users with complementary attributes and exposes plaintext that neither user is authorized to read alone.

The record

CVE
CVE-2021-37588
Published
Jul 27, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-327, T1140
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 27, 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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.9NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
4.3NIST NVDAV:N/AC:M/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)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-327Use of a Broken or Risky Cryptographic Algorithm
T1140Deobfuscate/Decode Files or Information

Public exploit references

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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