CVE-2019-11766: dhcp6.c in dhcpcd before 6.11.7 and 7.x before 7.2.2 has a buffer over-read in the D6_OPTION_PD_EXCLUDE featur

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CRITICAL 9.8REMOTEWATCHLISTUPGRADEMITIGATE

CVE-2019-11766 is a critical-severity flaw (CVSS 9.8) affecting dhcpcd, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

dhcp6.c in dhcpcd before 6.11.7 and 7.x before 7.2.2 has a buffer over-read in the D6_OPTION_PD_EXCLUDE feature.

Why this priority

Critical severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.0% (top 19%)
CISA exploited list	No
Weakness	CWE-125
Published	2019-05-05
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: debian · dhcpcd project

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

Am I affected?

Timeline

2019-05-05 06:29 UTCPublished CVE record published
2026-06-17 02:13 UTCUpdated Record last modified

dhcpcd project dhcpcd UPGRADE

Affected: < 6.11.7 · >= 7.0.0 and < 7.2.2

Fixed in: 6.11.7, 7.2.2

Safe to downgrade to: a release before 7.0.0

1. Check installed version

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

2. UPGRADE to 6.11.7 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade dhcpcd

Note

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

3. If no update is available yet, DOWNGRADE to a release before 7.0.0 (Debian / Ubuntu)

apt-cache madison dhcpcd sudo apt install dhcpcd=<VERSION_BEFORE_7.0.0> sudo apt-mark hold dhcpcd

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list dhcpcd sudo dnf downgrade dhcpcd-<VERSION_BEFORE_7.0.0> sudo dnf versionlock add dhcpcd

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.

debian debian linux MITIGATE

Affected: 8.0 · 9.0 · 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

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-2019-11766?

dhcpcd: upgrade to 6.11.7, 7.2.2; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2019-11766 being exploited?

CVE-2019-11766 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-2019-11766 affect?

CVE-2019-11766 affects dhcpcd, debian linux. Severity is critical (CVSS 9.8). dhcp6.c in dhcpcd before 6.11.7 and 7.x before 7.2.2 has a buffer over-read in the D6_OPTION_PD_EXCLUDE feature.

How urgent is CVE-2019-11766?

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

Software pages

Debian vulnerabilities

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References

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