CVE-2021-3183: Files.com Fat Client 3.3.6 allows authentication bypass because the client continues to have access after a lo

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HIGH 7.5REMOTEDOWNGRADE

CVE-2021-3183 is a high-severity flaw (CVSS 7.5) affecting fat client. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Files.com Fat Client 3.3.6 allows authentication bypass because the client continues to have access after a logout and a removal of a login profile.

Why this priority

High severity
Remotely exploitable, no login, no user action

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

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.4% (top 27%)
CISA exploited list	No
Weakness	CWE-613
Published	2021-01-19
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: files

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

Am I affected?

Timeline

2021-01-19 15:15 UTCPublished CVE record published
2026-06-17 04:04 UTCUpdated Record last modified

files fat client DOWNGRADE

Affected: 3.3.6

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.3.6

1. Check installed version

apt-cache policy fat-client || rpm -q fat-client || fat-client --version

2. No fixed release: DOWNGRADE to a release before 3.3.6 (Debian / Ubuntu)

apt-cache madison fat-client sudo apt install fat-client=<VERSION_BEFORE_3.3.6> sudo apt-mark hold fat-client

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

dnf --showduplicates list fat-client sudo dnf downgrade fat-client-<VERSION_BEFORE_3.3.6> sudo dnf versionlock add fat-client

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.

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-2021-3183?

fat client: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-3183 being exploited?

CVE-2021-3183 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-2021-3183 affect?

CVE-2021-3183 affects fat client. Severity is high (CVSS 7.5). Files.com Fat Client 3.3.6 allows authentication bypass because the client continues to have access after a logout and a removal of a login profile.

How urgent is CVE-2021-3183?

Priority 50/100. High severity; Remotely exploitable, no login, no user action

References

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