dbcve.org
SingularityApplication · Sylabs

CVE-2021-33027

CRITICAL · 9.8 CVSS v3.1 Published 2021-07-19
Fix available
A fix is available. Upgrade to 1.2.6 / 1.3.4 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Sylabs Singularity Enterprise through 1.6.2 has Insufficient Entropy in a nonce.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

Sylabs Singularity Enterprise through version 1.6.2 uses a cryptographically weak nonce generation mechanism with insufficient entropy. This means the random values used for authentication, session management, or other security-critical operations can be predicted or brute-forced, potentially allowing attackers to forge tokens, hijack sessions, or bypass authentication controls.

MitigationUpgrade to a patched version of Singularity Enterprise. If no patch is available, ensure the system has access to high-quality entropy sources (e.g., hardware RNG) and consider regenerating any session tokens or authentication credentials that may have been generated by the vulnerable version.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
SingularityApplication
Affected:>= 1.2.0, < 1.2.6>= 1.3.0, < 1.3.4>= 1.4.0, < 1.4.4>= 1.5.0, < 1.5.4>= 1.6.0, < 1.6.3

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Singularity Enterprise version
    Run `singularity --version` or check the product's web interface for its version information
    Affected if The version falls within these ranges: >=1.2.0 and <1.2.6; >=1.3.0 and <1.3.4; >=1.4.0 and <1.4.4; >=1.5.0 and <1.5.4; >=1.6.0 and <1.6.3
  2. Determine if web portal or API is enabled
    Inspect whether the Singularity Enterprise web portal or REST API is exposed and accessible
    Affected if The web interface or API is reachable over the network, as the weak nonce generation affects authentication and session tokens used by these interfaces
  3. Verify entropy sources on the host system
    Check available entropy sources by examining /proc/sys/kernel/random/entropy_avail or running `cat /dev/urandom` test, and check if a hardware RNG (RNGD) service is running
    Affected if The system has insufficient entropy (below 256 bits available) and lacks a hardware random number generator, which compounds the weak nonce generation vulnerability
  4. Review authentication tokens in use
    Examine active session tokens or JWTs generated by the system if accessible in logs or configuration
    Affected if Session tokens appear to have low entropy patterns or can be observed being generated with predictable structures

You are affected if the installed Singularity Enterprise version is within any of the vulnerable ranges listed AND the web portal or API is exposed, especially on systems with limited entropy sources.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.2.6 / 1.3.4 / 1.4.4 or later
Fixed in 1.2.61.3.41.4.4
Interim mitigation

Upgrade to a patched version of Singularity Enterprise. If no patch is available, ensure the system has access to high-quality entropy sources (e.g., hardware RNG) and consider regenerating any session tokens or authentication credentials that may have been generated by the vulnerable version.

Recommended fix Moderate confidence

Singularity 1.6.3 or later (latest stable release)

  1. 1. Identify your current Singularity version using: singularity --version
  2. 2. Review the Singularity release notes at support.sylabs.io for version 1.6.3 or later to confirm the CVE-2021-33027 fix
  3. 3. Download the latest stable Singularity release from the official Sylabs repository or build from source
  4. 4. Install the upgraded version following standard installation procedures for your platform
  5. 5. Verify the installation by running: singularity --version
  6. 6. Test that your containers and workflows function correctly with the updated version
Caveat Review release notes for any behavior changes between your current version and the upgrade target; major version upgrades may have breaking changes

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Singularity Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-33027 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data