CVE-2021-3374: Directory traversal in RStudio Shiny Server before 1.5.16 allows attackers to read the application source code

Q: How do I fix CVE-2021-3374?

shiny server: upgrade to 1.5.16. Exact commands for each OS are on this page.

Q: Is CVE-2021-3374 being exploited?

CVE-2021-3374 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-3374 affect?

CVE-2021-3374 affects shiny server. Severity is medium (CVSS 5.3). Directory traversal in RStudio Shiny Server before 1.5.16 allows attackers to read the application source code, involving an encoded slash.

Q: How urgent is CVE-2021-3374?

Priority 53/100. EPSS top 3%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

This week

MEDIUM 5.3REMOTEUPGRADE

CVE-2021-3374 is a medium-severity flaw (CVSS 5.3) affecting shiny server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Directory traversal in RStudio Shiny Server before 1.5.16 allows attackers to read the application source code, involving an encoded slash.

Why this priority

EPSS top 3%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	14.8% (top 3%)
CISA exploited list	No
Weakness	CWE-22
Published	2021-04-02
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: rstudio

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-04-02 19:15 UTCPublished CVE record published
2026-06-17 04:04 UTCUpdated Record last modified

rstudio shiny server UPGRADE

Affected: < 1.5.16

Fixed in: 1.5.16

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy shiny-server || rpm -q shiny-server || shiny-server --version

2. UPGRADE to 1.5.16 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade shiny-server

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade shiny-server

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Nuclei scan template: Rstudio Shiny Server <1.5.16 - Local File Inclusion

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-3374?

shiny server: upgrade to 1.5.16. Exact commands for each OS are on this page.

Is CVE-2021-3374 being exploited?

CVE-2021-3374 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-3374 affect?

CVE-2021-3374 affects shiny server. Severity is medium (CVSS 5.3). Directory traversal in RStudio Shiny Server before 1.5.16 allows attackers to read the application source code, involving an encoded slash.

How urgent is CVE-2021-3374?

Priority 53/100. EPSS top 3%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

References

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