CVE-2026-73549
Received Received - Intake

Denial of Service in Envoy Proxy via IPv6 Scope Parsing

Publication date: 2026-09-21

Last updated on: 2026-09-21

Assigner: GitHub, Inc.

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.

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Meta Information

Published
2026-09-21
Last Modified
2026-09-21
Generated
2026-09-22
AI Q&A
2026-09-21
EPSS Evaluated
N/A
NVD
CVE-2026-73549
EUVD
EUVD-2026-84108

Affected Vendors & Products

Showing 8 associated CPEs
Vendor Product Version / Range
envoy envoy 1.36.10
envoy envoy 1.37.6
envoy envoy 1.38.4
envoy envoy 1.39.1
envoyproxy envoy 1.36.10
envoyproxy envoy 1.37.6
envoyproxy envoy 1.38.4
envoyproxy envoy 1.39.1

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-754 The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product.

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Executive Summary

CVE-2026-73549 is a vulnerability in Envoy Proxy where improper handling of scoped IPv6 addresses causes crashes. The issue occurs when Envoy processes IPv6 addresses with scope identifiers (e.g., fe80::1%1) in QUIC requests or ORIGINAL_DST transparent-proxy deployments. The function copyInternetAddressAndPort converts the address to a string and then parses it back, but inet_pton cannot handle the %scope_id suffix, leading to exceptions or process termination.

Detection Guidance

To detect this vulnerability, monitor Envoy proxy logs for crashes or exceptions when processing IPv6 addresses with scope identifiers (e.g., fe80::1%1). Check for QUIC request failures or process aborts in transparent proxy deployments using ORIGINAL_DST.

Impact Analysis

This vulnerability can cause denial-of-service conditions by crashing Envoy Proxy processes. It affects deployments using QUIC requests with scoped IPv6 addresses or transparent proxy setups where the kernel provides scoped IPv6 destinations. The impact is process termination, leading to service disruption for affected traffic.

Compliance Impact

This vulnerability primarily causes denial-of-service conditions by crashing Envoy proxy instances when processing scoped IPv6 addresses. While it does not directly violate GDPR or HIPAA, such crashes could disrupt data processing or transmission, potentially impacting compliance with availability requirements in these regulations.

Mitigation Strategies

Upgrade Envoy to versions 1.36.10, 1.37.6, 1.38.4, or 1.39.1 or later. If upgrading is not immediately possible, disable QUIC support or block IPv6 link-local traffic with scope IDs in transparent proxy configurations.

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