CVE-2020-13846 — singularity
HIGHCVE-2020-13846 is a high-severity (CVSS 7.5) vulnerability in github.com/sylabs/singularity. A fix is available for github.com/sylabs/singularity — see the affected versions and patch details below.
"Verify All" Returns Success Despite Validation Failures in Singularity
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2020-13846 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/sylabs/singularityReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Impact
The --all / -a option to singularity verify returns success even when some objects in a SIF container are not signed, or cannot be verified.
The SIF objects that are not verified are reported in WARNING log messages, but a Container Verified message and exit code of 0 are returned.
Workflows that verify a container using --all / -a and use the exit code as an indicator of success are vulnerable to running SIF containers that have unsigned, or modified, objects that may be exploited to introduce malicious behavior.
$ singularity verify -a image.sif
WARNING: Missing signature for SIF descriptor 2 (JSON.Generic)
WARNING: Missing signature for SIF descriptor 3 (FS)
Container is signed by 1 key(s):
Verifying partition: Def.FILE:
12045C8C0B1004D058DE4BEDA20C27EE7FF7BA84
[LOCAL] Unit Test <[email protected]>
[OK] Data integrity verified
INFO: Container verified: image.sif
$ echo $?
0
Patches
Singularity 3.6.0 has a new implementation of sign/verify that fixes this issue.
All users are advised to upgrade to 3.6.0. Note that Singularity 3.6.0 uses a new signature format that is necessarily incompatible with Singularity < 3.6.0 - e.g. Singularity 3.5.3 cannot verify containers signed by 3.6.0.
Version 3.6.0 includes a --legacy-insecure flag for the singularity verify command, that will perform verification of the older, and insecure, legacy signatures for compatibility with existing containers. This does not guarantee that containers have not been modified since signing, due to other issues in the legacy signature format.
Workarounds
If you are unable to update to 3.6.0 ensure that you do not rely on the return code of singularity verify --all / -a as an indicator of trust in a container.
Note that other issues in the sign/verify implementation in Singularity < 3.6.0 allow additional means to introduce malicious behavior to a signed container.
For more information
General questions about the impact of the advisory / changes made in the 3.6.0 release can be asked in the:
Any sensitive security concerns should be directed to: [email protected]
See our Security Policy here: https://sylabs.io/security-policy
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/sylabs/singularity | ≥ 3.5.0&&< 3.6.0 | 3.6.0go get github.com/sylabs/singularity@v3.6.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/sylabs/singularity, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/sylabs/singularity to 3.6.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-13846 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2020-13846 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2020-13846. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2020-13846 in your dependencies?
O3 Security finds CVE-2020-13846 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.