CVE-2026-73551: Envoy is an open source edge and service proxy designed for cloud-native applications

Routine

MEDIUM 5.3REMOTEUPGRADE

CVE-2026-73551 is a medium-severity flaw (CVSS 5.3) affecting envoy. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy's URL normalization does not recognize dot and dotdot path segments when they carry semicolon parameters. A request such as /user/..;foo=bar/admin is therefore not canonicalized to /admin even when path normalization is enabled. If an upstream interprets the segment according to RFC 3986 while Envoy applies ro

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 56%)
CISA exploited list	No
Weakness	CWE-647
Published	2026-09-21
Last modified	2026-10-05

Publisher (CNA): GitHub, Inc. · Vendor: envoyproxy

Last updated 2026-10-05 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-21 21:17 UTCPublished CVE record published
2026-10-05 14:06 UTCUpdated Record last modified

envoyproxy envoy UPGRADE

Affected: < 1.36.10 · >= 1.37.0 and < 1.37.6 · >= 1.38.0 and < 1.38.4 · >= 1.39.0 and < 1.39.1

Fixed in: 1.36.10, 1.37.6, 1.38.4, 1.39.1

Safe to downgrade to: a release before 1.37.0

1. Check installed version

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

2. UPGRADE to 1.36.10 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade envoy

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 1.37.0 (Debian / Ubuntu)

apt-cache madison envoy sudo apt install envoy=<VERSION_BEFORE_1.37.0> sudo apt-mark hold envoy

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

dnf --showduplicates list envoy sudo dnf downgrade envoy-<VERSION_BEFORE_1.37.0> sudo dnf versionlock add envoy

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-2026-73551?

envoy: upgrade to 1.36.10, 1.37.6, 1.38.4, 1.39.1. Exact commands for each OS are on this page.

Is CVE-2026-73551 being exploited?

CVE-2026-73551 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-2026-73551 affect?

CVE-2026-73551 affects envoy. Severity is medium (CVSS 5.3). Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy's URL normalization does not recognize dot and dotdot path segments when they carry semicolon paramet

How urgent is CVE-2026-73551?

Priority 35/100. Remotely exploitable, no login, no user action

Software pages

Envoy vulnerabilities

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References

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