CVE-2020-29577: The official znc docker images before 1.7.1-slim contain a blank password for a root user

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CRITICAL 9.8REMOTEWATCHLISTDOWNGRADE

CVE-2020-29577 is a critical-severity flaw (CVSS 9.8) affecting znc docker image. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The official znc docker images before 1.7.1-slim contain a blank password for a root user. Systems using the znc docker container deployed by affected versions of the Docker image may allow an remote attacker to achieve root access with a blank password.

Why this priority

Critical severity
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	2.3% (top 17%)
CISA exploited list	No
Published	2020-12-08
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: znc

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

Am I affected?

Timeline

2020-12-08 16:15 UTCPublished CVE record published
2026-06-17 03:11 UTCUpdated Record last modified

znc znc docker image DOWNGRADE

Affected: 1.6 · 1.6-slim · 1.6.4 · 1.6.4-slim · 1.6.5 · 1.6.5-slim · 1.6.6 · 1.6.6-slim

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.6

1. Check installed version

apt-cache policy znc-docker-image || rpm -q znc-docker-image || znc-docker-image --version

2. No fixed release: DOWNGRADE to a release before 1.6 (Debian / Ubuntu)

apt-cache madison znc-docker-image sudo apt install znc-docker-image=<VERSION_BEFORE_1.6> sudo apt-mark hold znc-docker-image

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

dnf --showduplicates list znc-docker-image sudo dnf downgrade znc-docker-image-<VERSION_BEFORE_1.6> sudo dnf versionlock add znc-docker-image

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-2020-29577?

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

Is CVE-2020-29577 being exploited?

CVE-2020-29577 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-2020-29577 affect?

CVE-2020-29577 affects znc docker image. Severity is critical (CVSS 9.8). The official znc docker images before 1.7.1-slim contain a blank password for a root user. Systems using the znc docker container deployed by affected versions of the Docker image may allow an remote attacker to achieve root access with a b

How urgent is CVE-2020-29577?

Priority 65/100. Critical severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

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References

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