CVE-2017-8900: LightDM through 1.22.0, when systemd is used in Ubuntu 16.10 and 17.x, allows physically proximate attackers t

Q: How do I fix CVE-2017-8900?

lightdm: upgrade to newer than 1.22.0. Exact commands for each OS are on this page.

Q: Is CVE-2017-8900 being exploited?

CVE-2017-8900 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-2017-8900 affect?

CVE-2017-8900 affects lightdm. Severity is medium (CVSS 4.6). LightDM through 1.22.0, when systemd is used in Ubuntu 16.10 and 17.x, allows physically proximate attackers to bypass intended AppArmor restrictions and visit the home directories of arbitrary users by establishing a guest session.

Q: How urgent is CVE-2017-8900?

Priority 30/100. On your watchlist

Routine

MEDIUM 4.6WATCHLISTUPGRADE

CVE-2017-8900 is a medium-severity flaw (CVSS 4.6) affecting lightdm. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

LightDM through 1.22.0, when systemd is used in Ubuntu 16.10 and 17.x, allows physically proximate attackers to bypass intended AppArmor restrictions and visit the home directories of arbitrary users by establishing a guest session.

Why this priority

On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	4.6 (Medium)
Attack vector	Physical
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 64%)
CISA exploited list	No
Published	2017-05-12
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: lightdm project

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

Am I affected?

Timeline

2017-05-12 07:29 UTCPublished CVE record published
2026-06-17 01:27 UTCUpdated Record last modified

lightdm project lightdm UPGRADE

Affected: <= 1.22.0

Fixed in: newer than 1.22.0

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 1.22.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade lightdm

Note

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

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-2017-8900?

lightdm: upgrade to newer than 1.22.0. Exact commands for each OS are on this page.

Is CVE-2017-8900 being exploited?

CVE-2017-8900 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-2017-8900 affect?

CVE-2017-8900 affects lightdm. Severity is medium (CVSS 4.6). LightDM through 1.22.0, when systemd is used in Ubuntu 16.10 and 17.x, allows physically proximate attackers to bypass intended AppArmor restrictions and visit the home directories of arbitrary users by establishing a guest session.

How urgent is CVE-2017-8900?

Priority 30/100. On your watchlist

Software pages

Ubuntu vulnerabilities

Related CVEs

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CVE-2015-8316 MEDIUM 5.9 DOWNGRADE Array index error in LightDM (aka Light Display Manager) 1.14.3, 1.16.x before 1.16.6 when the XDMCP server is
CVE-2011-3349 HIGH 7.8 UPGRADE lightdm before 0.9.6 writes in .dmrc and Xauthority files using root permissions while the files are in user c

References

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