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CRITICAL severity

CVE-2019-9901 — envoy

CRITICALFix: envoyproxy/envoy@e668e66

CVE-2019-9901 is a critical-severity (CVSS 10) CWE-706 vulnerability in github.com/envoyproxy/envoy. A fix is available for github.com/envoyproxy/envoy — see the affected versions and patch details below.

EnvoyProxy Envoy Missing HTTP URL path normalization

Also known asGHSA-2wmf-p7f8-w42hGHSA-xcx5-93pw-jw2w
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
5.0%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs92th percentile — riskier than 92% of all scored CVEsHighest risk
0.00%2.14%4.27%6.41%0.1%5.0%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐹github.com/envoyproxy/envoy

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Envoy 1.9.0 and before does not normalize HTTP URL paths. A remote attacker may craft a relative path, e.g., something/../admin, to bypass access control, e.g., a block on /admin. A backend server could then interpret the non-normalized path and provide an attacker access beyond the scope provided for by the access control policy.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/envoyproxy/envoyall versions1.9.1go get github.com/envoyproxy/envoy@v1.9.1

Affected Products

1 product · 1 configurations
Application
envoyenvoyproxy
≤ 1.9.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/envoyproxy/envoy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/envoyproxy/envoy to 1.9.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-9901 is resolved across your whole dependency graph.

  3. Workarounds

    Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant
ProductFixed inAdvisory
OpenShift Service Mesh Tech Previewservicemesh-proxy-0:0.9.1-1.el7RHSA-2019:0741

Frequently Asked Questions

Envoy 1.9.0 and before does not normalize HTTP URL paths. A remote attacker may craft a relative path, e.g., something/../admin, to bypass access control, e.g., a block on /admin. A backend server could then interpret the non-normalized path and provide an attacker access beyond the scope provided for by the access control policy.
O3 Security · Impact-Aware SCA

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CVE-2019-9901: envoy — Fixed in 1.9.1