CVE-2019-14809: net/url in Go before 1.11.13 and 1.12.x before 1.12.8 mishandles malformed hosts in URLs, leading to an author

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CRITICAL 9.8REMOTEWATCHLISTUPGRADEMITIGATE

CVE-2019-14809 is a critical-severity flaw (CVSS 9.8) affecting go, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

net/url in Go before 1.11.13 and 1.12.x before 1.12.8 mishandles malformed hosts in URLs, leading to an authorization bypass in some applications. This is related to a Host field with a suffix appearing in neither Hostname() nor Port(), and is related to a non-numeric port number. For example, an attacker can compose a crafted javascript:// URL that results in a hostname of google.com.

Why this priority

Critical severity
EPSS top 5%: very likely to be exploited
Public exploit reference
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	8.4% (top 5%)
CISA exploited list	No
Published	2019-08-13
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: debian · golang

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

Am I affected?

Timeline

2019-08-13 21:15 UTCPublished CVE record published
2026-06-17 02:19 UTCUpdated Record last modified

golang go UPGRADE

Affected: < 1.11.13 · >= 1.12.0 and < 1.12.8

Fixed in: 1.11.13, 1.12.8

Safe to downgrade to: a release before 1.12.0

1. Check installed version

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

2. UPGRADE to 1.11.13 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade go

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 1.12.0 (Debian / Ubuntu)

apt-cache madison go sudo apt install go=<VERSION_BEFORE_1.12.0> sudo apt-mark hold go

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

dnf --showduplicates list go sudo dnf downgrade go-<VERSION_BEFORE_1.12.0> sudo dnf versionlock add go

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: 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.0

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.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · root · FIXED · 6.40.04-7.fc46 · FEDORA-2026-7329868400 · source

sudo dnf upgrade --advisory=FEDORA-2026-7329868400

RHEL 7 · golang · DEFERRED

Alpine 3.20 · go · FIXED · go-1.12.8-r0

apk add --upgrade go apk info -v go

Alpine 3.21 · go · FIXED · go-1.12.8-r0

apk add --upgrade go apk info -v go

Alpine 3.22 · go · FIXED · go-1.12.8-r0

apk add --upgrade go apk info -v go

Alpine 3.23 · go · FIXED · go-1.12.8-r0

apk add --upgrade go apk info -v go

Amazon Linux 2 · see advisory · FIXED · ALAS2-2019-1309 · source

sudo yum update --advisory=ALAS2-2019-1309

Amazon Linux 1 · see advisory · FIXED · ALAS-2019-1270 · source

sudo yum update --advisory=ALAS-2019-1270

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-2019-14809?

go: upgrade to 1.11.13, 1.12.8; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2019-14809 being exploited?

CVE-2019-14809 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-2019-14809 affect?

CVE-2019-14809 affects go, debian linux. Severity is critical (CVSS 9.8). net/url in Go before 1.11.13 and 1.12.x before 1.12.8 mishandles malformed hosts in URLs, leading to an authorization bypass in some applications. This is related to a Host field with a suffix appearing in neither Hostname() nor Port(), and

How urgent is CVE-2019-14809?

Priority 73/100. Critical severity; EPSS top 5%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Go (Golang) vulnerabilities · Debian vulnerabilities

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References

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