CVE-2022-25226: ThinVNC version 1.0b1 allows an unauthenticated user to bypass the authentication process via 'http://thin-vnc

This week

CRITICAL 10.0REMOTEDOWNGRADE

CVE-2022-25226 is a critical-severity flaw (CVSS 10.0) affecting thinvnc. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

ThinVNC version 1.0b1 allows an unauthenticated user to bypass the authentication process via 'http://thin-vnc:8080/cmd?cmd=connect' by obtaining a valid SID without any kind of authentication. It is possible to achieve code execution on the server by sending keyboard or mouse events to the server.

Why this priority

Critical severity
EPSS top 4%: 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	10.0 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	11.0% (top 4%)
CISA exploited list	No
Published	2022-04-18
Last modified	2026-06-17

Publisher (CNA): Fluid Attacks · Vendor: cybelsoft

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

Am I affected?

Timeline

2022-04-18 17:15 UTCPublished CVE record published
2026-06-17 04:33 UTCUpdated Record last modified

cybelsoft thinvnc DOWNGRADE

Affected: 1.0 b1

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.0 (Debian / Ubuntu)

apt-cache madison thinvnc sudo apt install thinvnc=<VERSION_BEFORE_1.0> sudo apt-mark hold thinvnc

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

dnf --showduplicates list thinvnc sudo dnf downgrade thinvnc-<VERSION_BEFORE_1.0> sudo dnf versionlock add thinvnc

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.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · iodine · FIXED · 0.9.0-2.fc46 · FEDORA-2026-4448545972 · source

sudo dnf upgrade --advisory=FEDORA-2026-4448545972

Fedora ELN · python-idna · FIXED · 3.20-1.eln159 · FEDORA-2026-4421e6642f · source

sudo dnf upgrade --advisory=FEDORA-2026-4421e6642f

Public exploits and detection

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

GitHub PoC: krill-x7/CVE-2022-25226 (1 stars)
Write-up: fluidattacks.com/advisories/sinatra/
Nuclei scan template: ThinVNC - Authentication Bypass

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-2022-25226?

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

Is CVE-2022-25226 being exploited?

CVE-2022-25226 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-2022-25226 affect?

CVE-2022-25226 affects thinvnc. Severity is critical (CVSS 10.0). ThinVNC version 1.0b1 allows an unauthenticated user to bypass the authentication process via 'http://thin-vnc:8080/cmd?cmd=connect' by obtaining a valid SID without any kind of authentication. It is possible to achieve code execution on th

How urgent is CVE-2022-25226?

Priority 69/100. Critical severity; EPSS top 4%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

References

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