CVE-2021-23409: The package github.com/pires/go-proxyproto before 0.6.0 are vulnerable to Denial of Service (DoS) via creating

Q: How do I fix CVE-2021-23409?

go-proxyproto: upgrade to 0.6.0. Exact commands for each OS are on this page.

Q: Is CVE-2021-23409 being exploited?

CVE-2021-23409 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-2021-23409 affect?

CVE-2021-23409 affects go-proxyproto. Severity is high (CVSS 7.5). The package github.com/pires/go-proxyproto before 0.6.0 are vulnerable to Denial of Service (DoS) via creating connections without the proxy protocol header.

Q: How urgent is CVE-2021-23409?

Priority 50/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADE

CVE-2021-23409 is a high-severity flaw (CVSS 7.5) affecting go-proxyproto. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The package github.com/pires/go-proxyproto before 0.6.0 are vulnerable to Denial of Service (DoS) via creating connections without the proxy protocol header.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.6% (top 24%)
CISA exploited list	No
Published	2021-07-21
Last modified	2026-06-17

Publisher (CNA): Snyk · Vendor: go-proxyproto project

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

Am I affected?

Timeline

2021-07-21 07:15 UTCPublished CVE record published
2026-06-17 03:38 UTCUpdated Record last modified

go-proxyproto project go-proxyproto UPGRADE

Affected: < 0.6.0

Fixed in: 0.6.0

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 0.6.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade go-proxyproto

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-2021-23409?

go-proxyproto: upgrade to 0.6.0. Exact commands for each OS are on this page.

Is CVE-2021-23409 being exploited?

CVE-2021-23409 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-2021-23409 affect?

CVE-2021-23409 affects go-proxyproto. Severity is high (CVSS 7.5). The package github.com/pires/go-proxyproto before 0.6.0 are vulnerable to Denial of Service (DoS) via creating connections without the proxy protocol header.

How urgent is CVE-2021-23409?

Priority 50/100. High severity; Remotely exploitable, no login, no user action

Software pages

GitHub vulnerabilities

Related CVEs

CVE-2021-23351 MEDIUM 4.4 UPGRADE MITIGATE The package github.com/pires/go-proxyproto before 0.5.0 are vulnerable to Denial of Service (DoS) via the pars

References

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