CVE-2019-3464: Insufficient sanitization of environment variables passed to rsync can bypass the restrictions imposed by rssh

This week

CRITICAL 9.8REMOTEWATCHLISTDOWNGRADEMITIGATEMITIGATE

CVE-2019-3464 is a critical-severity flaw (CVSS 9.8) affecting rssh, debian linux, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Insufficient sanitization of environment variables passed to rsync can bypass the restrictions imposed by rssh, a restricted shell that should restrict users to perform only rsync operations, resulting in the execution of arbitrary shell commands.

Why this priority

Critical severity
EPSS top 8%: very likely to be exploited
Remotely exploitable, no login, no user action
On your watchlist

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	4.7% (top 8%)
CISA exploited list	No
Weakness	CWE-665
Published	2019-02-06
Last modified	2026-06-17

Publisher (CNA): Debian GNU/Linux · Vendor: canonical · debian · fedoraproject · pizzashack

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

Am I affected?

Timeline

2019-02-06 19:29 UTCPublished CVE record published
2026-06-17 02:35 UTCUpdated Record last modified

pizzashack rssh DOWNGRADE

Affected: 2.3.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.3.4

1. Check installed version

apt-cache policy rssh || rpm -q rssh || rssh --version

2. No fixed release: DOWNGRADE to a release before 2.3.4 (Debian / Ubuntu)

apt-cache madison rssh sudo apt install rssh=<VERSION_BEFORE_2.3.4> sudo apt-mark hold rssh

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list rssh sudo dnf downgrade rssh-<VERSION_BEFORE_2.3.4> sudo dnf versionlock add rssh

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

debian debian linux MITIGATE

Affected: 8.0 · 9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

fedoraproject fedora MITIGATE

Affected: 29 · 30 · 31

Fixed in: no fixed release known

Safe to downgrade to: a release before 29

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

canonical ubuntu linux MITIGATE

Affected: 14.04 · 16.04 · 18.04 · 18.10

Fixed in: no fixed release known

Safe to downgrade to: a release before 14.04

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

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-2019-3464?

rssh: downgrade or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2019-3464 being exploited?

CVE-2019-3464 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-2019-3464 affect?

CVE-2019-3464 affects rssh, debian linux, fedora. Severity is critical (CVSS 9.8). Insufficient sanitization of environment variables passed to rsync can bypass the restrictions imposed by rssh, a restricted shell that should restrict users to perform only rsync operations, resulting in the execution of arbitrary shell co

How urgent is CVE-2019-3464?

Priority 67/100. Critical severity; EPSS top 8%: very likely to be exploited; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Ubuntu vulnerabilities · Debian vulnerabilities

Related CVEs

CVE-2019-3463 CRITICAL 9.8 DOWNGRADE MITIGATE Insufficient sanitization of arguments passed to rsync can bypass the restrictions imposed by rssh, a restrict
CVE-2019-1000018 HIGH 7.8 DOWNGRADE MITIGATE rssh version 2.3.4 contains a CWE-77: Improper Neutralization of Special Elements used in a Command ('Command

References

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