CVE-2021-32635 | Action Commands (run/shell/exec) Against Library URIs Ignore Configured Remote Endpoint

Singularity is an open source container platform. In verions 3.7.2 and 3.7.3, Dde to incorrect use of a default URL, `singularity` action commands (`run`/`shell`/`exec`) specifying a container using a `library://` URI will always attempt to retrieve the container from the default remote endpoint (`cloud.sylabs.io`) rather than the configured remote endpoint. An attacker may be able to push a malicious container to the default remote endpoint with a URI that is identical to the URI used by a victim with a non-default remote endpoint, thus executing the malicious container. Only action commands (`run`/`shell`/`exec`) against `library://` URIs are affected. Other commands such as `pull` / `push` respect the configured remote endpoint. The vulnerability is patched in Singularity version 3.7.4. Two possible workarounds exist: Users can only interact with the default remote endpoint, or an installation can have an execution control list configured to restrict execution to containers signed with specific secure keys.

Published: 2021-05-28 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-32635 is rated Moderate Risk (49.5/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.63%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-32635

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-04-28 0.54% 0.63% +0.09%
2 2025-03-30 0.83% 0.54% -0.29%
3 2025-03-29 — 0.83% —

Full EPSS history (13 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-32635

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 2.8 3.4 [email protected]
6.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 2.8 3.4 [email protected]
6.8 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 6.4 [email protected]

Weakness enumeration for CVE-2021-32635

GitHub Security Advisory for CVE-2021-32635

GHSA-5mv9-q7fq-9394 · Severity: medium · Ecosystem: go — Action Commands (run/shell/exec) Against Library URIs Ignore Configured Remote Endpoint

OS Trackers for CVE-2021-32635

vendor priority summary link
alpine medium CVE-2021-32635: 1 source package rows (singularity); 7 state rows across 5 repos (3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 5, open 2. https://security.alpinelinux.org/vuln/CVE-2021-32635
debian unimportant CVE-2021-32635 unimportant priority: Debian including 1 source packages (singularity-container), 1 status rows across 1 suites (sid): resolved 1. https://security-tracker.debian.org/tracker/CVE-2021-32635
gentoo high CVE-2021-32635: 1 GLSA(s) (202107-50), 1 atom(s) (sys-cluster/singularity); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-32635
ubuntu medium CVE-2021-32635 medium priority: Ubuntu including 1 source packages (singularity-container), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 9, needs-triage 4, ignored 3. https://ubuntu.com/security/CVE-2021-32635

Affected software / configurations for CVE-2021-32635

Vendor Product Version Raw CPE
sylabs singularity 3.7.2 cpe:2.3:a:sylabs:singularity:3.7.2:*:*:*:*:*:*:*
sylabs singularity 3.7.3 cpe:2.3:a:sylabs:singularity:3.7.3:*:*:*:*:*:*:*

References for CVE-2021-32635

cvelogic Threat Intelligence