CVE-2020-5404: The HttpClient from Reactor Netty, versions 0.9.x prior to 0.9.5, and versions 0.8.x prior to 0.8.16, may be u

Routine

MEDIUM 5.9UPGRADE

CVE-2020-5404 is a medium-severity flaw (CVSS 5.9) affecting reactor netty. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The HttpClient from Reactor Netty, versions 0.9.x prior to 0.9.5, and versions 0.8.x prior to 0.8.16, may be used incorrectly, leading to a credentials leak during a redirect to a different domain. In order for this to happen, the HttpClient must have been explicitly configured to follow redirects.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.7% (top 49%)
CISA exploited list	No
Weakness	CWE-522
Published	2020-03-03
Last modified	2026-09-04

Publisher (CNA): Pivotal Software, Inc. · Vendor: broadcom

Last updated 2026-09-04 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-03-03 18:15 UTCPublished CVE record published
2026-09-04 18:59 UTCUpdated Record last modified

broadcom reactor netty UPGRADE

Affected: >= 0.8.0 and <= 0.8.15 · >= 0.9.0 and <= 0.9.4

Fixed in: newer than 0.9.4

Safe to downgrade to: a release before 0.8.0

1. Check installed version

apt-cache policy reactor-netty || rpm -q reactor-netty || reactor-netty --version

2. UPGRADE to newer than 0.9.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade reactor-netty

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade reactor-netty

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 0.8.0 (Debian / Ubuntu)

apt-cache madison reactor-netty sudo apt install reactor-netty=<VERSION_BEFORE_0.8.0> sudo apt-mark hold reactor-netty

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

dnf --showduplicates list reactor-netty sudo dnf downgrade reactor-netty-<VERSION_BEFORE_0.8.0> sudo dnf versionlock add reactor-netty

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-2020-5404?

reactor netty: upgrade to newer than 0.9.4. Exact commands for each OS are on this page.

Is CVE-2020-5404 being exploited?

CVE-2020-5404 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-2020-5404 affect?

CVE-2020-5404 affects reactor netty. Severity is medium (CVSS 5.9). The HttpClient from Reactor Netty, versions 0.9.x prior to 0.9.5, and versions 0.8.x prior to 0.8.16, may be used incorrectly, leading to a credentials leak during a redirect to a different domain. In order for this to happen, the HttpClien

How urgent is CVE-2020-5404?

Priority 34/100. No elevated risk signals yet.

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References

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