CVE-2021-33027Network attack vector

Authentication replay protection weakened by predictable nonce

Published Jul 19, 2021 · Updated Aug 3, 2024

Insufficient entropy in Sylabs Singularity Enterprise 1.6.2 and earlier allows remote attackers to weaken authentication replay protection. The bundled satori/go.uuid module generates non-random Version 4 UUIDs, and Singularity Enterprise places those values in OpenID Connect authentication requests as nonces. No authentication or user interaction is required, but Sylabs has not published a demonstrated consequence beyond weakened replay protection.

CVSS severity9.8
Critical
EPSS probability1.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient entropy in Sylabs Singularity Enterprise 1.6.2 and earlier allows remote attackers to weaken authentication replay protection. The bundled satori/go.uuid module generates non-random Version 4 UUIDs, and Singularity Enterprise places those values in OpenID Connect authentication requests as nonces. No authentication or user interaction is required, but Sylabs has not published a demonstrated consequence beyond weakened replay protection.

The record

CVE
CVE-2021-33027
Published
Jul 19, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-331, CAPEC-59
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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

7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NVDCVSS: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 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-331Insufficient Entropy
CAPEC-59Session Credential Falsification through Prediction

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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