CVE-2016-6866: slock allows attackers to bypass the screen lock via vectors involving an invalid password hash, which trigger

Q: How do I fix CVE-2016-6866?

slock: upgrade to newer than 1.3; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2016-6866 being exploited?

CVE-2016-6866 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-2016-6866 affect?

CVE-2016-6866 affects slock, fedora. Severity is high (CVSS 7.5). slock allows attackers to bypass the screen lock via vectors involving an invalid password hash, which triggers a NULL pointer dereference and crash.

Q: How urgent is CVE-2016-6866?

Priority 53/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADEMITIGATE

CVE-2016-6866 is a high-severity flaw (CVSS 7.5) affecting slock, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

slock allows attackers to bypass the screen lock via vectors involving an invalid password hash, which triggers a NULL pointer dereference and crash.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.9% (top 13%)
CISA exploited list	No
Weakness	CWE-476
Published	2017-02-15
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fedoraproject · suckless

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

Am I affected?

Timeline

2017-02-15 19:59 UTCPublished CVE record published
2026-06-17 00:51 UTCUpdated Record last modified

suckless slock UPGRADE

Affected: <= 1.3

Fixed in: newer than 1.3

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 1.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade slock

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade slock

Note

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

fedoraproject fedora MITIGATE

Affected: 24 · 25

Fixed in: no fixed release known

Safe to downgrade to: a release before 24

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-2016-6866?

slock: upgrade to newer than 1.3; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2016-6866 being exploited?

CVE-2016-6866 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-2016-6866 affect?

CVE-2016-6866 affects slock, fedora. Severity is high (CVSS 7.5). slock allows attackers to bypass the screen lock via vectors involving an invalid password hash, which triggers a NULL pointer dereference and crash.

How urgent is CVE-2016-6866?

Priority 53/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2020-36455 HIGH 8.1 UPGRADE An issue was discovered in the slock crate through 2020-11-17 for Rust
CVE-2012-1620 LOW 3.6 DOWNGRADE slock 0.9 does not properly handle the XRaiseWindow event when the screen is locked, which might allow physica

References

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