CVE-2015-8316: Array index error in LightDM (aka Light Display Manager) 1.14.3, 1.16.x before 1.16.6 when the XDMCP server is

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MEDIUM 5.9REMOTEWATCHLISTDOWNGRADE

CVE-2015-8316 is a medium-severity flaw (CVSS 5.9) affecting lightdm. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Array index error in LightDM (aka Light Display Manager) 1.14.3, 1.16.x before 1.16.6 when the XDMCP server is enabled allows remote attackers to cause a denial of service (process crash) via an XDMCP request packet with no address.

Why this priority

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	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	1.7% (top 22%)
CISA exploited list	No
Weakness	CWE-129
Published	2017-09-06
Last modified	2026-06-17

Publisher (CNA): Debian GNU/Linux · 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

2017-09-06 21:29 UTCPublished CVE record published
2026-06-17 00:34 UTCUpdated Record last modified

lightdm project lightdm DOWNGRADE

Affected: 1.14.3 · 1.16 · 1.16.1 · 1.16.2 · 1.16.3 · 1.16.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.14.3

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.14.3 (Debian / Ubuntu)

apt-cache madison lightdm sudo apt install lightdm=<VERSION_BEFORE_1.14.3> sudo apt-mark hold lightdm

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

dnf --showduplicates list lightdm sudo dnf downgrade lightdm-<VERSION_BEFORE_1.14.3> sudo dnf versionlock add lightdm

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-2015-8316?

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

Is CVE-2015-8316 being exploited?

CVE-2015-8316 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-2015-8316 affect?

CVE-2015-8316 affects lightdm. Severity is medium (CVSS 5.9). Array index error in LightDM (aka Light Display Manager) 1.14.3, 1.16.x before 1.16.6 when the XDMCP server is enabled allows remote attackers to cause a denial of service (process crash) via an XDMCP request packet with no address.

How urgent is CVE-2015-8316?

Priority 50/100. Remotely exploitable, no login, no user action; On your watchlist

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References

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