CVE-2019-9764: HashiCorp Consul 1.4.3 lacks server hostname verification for agent-to-agent TLS communication

This week

HIGH 7.4REMOTEDOWNGRADE

CVE-2019-9764 is a high-severity flaw (CVSS 7.4) affecting consul. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

HashiCorp Consul 1.4.3 lacks server hostname verification for agent-to-agent TLS communication. In other words, the product behaves as if verify_server_hostname were set to false, even when it is actually set to true. This is fixed in 1.4.4.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.4 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 51%)
CISA exploited list	No
Weakness	CWE-346
Published	2019-03-26
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: hashicorp

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

Am I affected?

Timeline

2019-03-26 14:29 UTCPublished CVE record published
2026-06-17 02:44 UTCUpdated Record last modified

hashicorp consul DOWNGRADE

Affected: 1.4.3

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.4.3

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.4.3 (Debian / Ubuntu)

apt-cache madison consul sudo apt install consul=<VERSION_BEFORE_1.4.3> sudo apt-mark hold consul

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

dnf --showduplicates list consul sudo dnf downgrade consul-<VERSION_BEFORE_1.4.3> sudo dnf versionlock add consul

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-2019-9764?

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

Is CVE-2019-9764 being exploited?

CVE-2019-9764 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-2019-9764 affect?

CVE-2019-9764 affects consul. Severity is high (CVSS 7.4). HashiCorp Consul 1.4.3 lacks server hostname verification for agent-to-agent TLS communication. In other words, the product behaves as if verify_server_hostname were set to false, even when it is actually set to true. This is fixed in 1.4.4

How urgent is CVE-2019-9764?

Priority 48/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

Consul vulnerabilities

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References

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