CVE-2026-73549 (CVSS 5.3)

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.

Is your site exposed to CVE-2026-73549?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

5.3

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0062

Probability of exploitation

0.48%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-754 CWE-754

References

Other References

Frequently Asked Questions

What is CVE-2026-73549? +

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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-73549? +

CVE-2026-73549 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0062, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-73549? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-0667

CWE-754: Improper Check for Unusual or Exceptional Conditions vulnerability that could cause arbitrary code execution, denial of service and loss …

CVE-2026-35225

An unauthenticated remote attacker is able to exhaust all available TCP connections in the CODESYS EtherNet/IP adapter stack, preventing legitimate …

CVE-2025-0112

A problem with a detection mechanism in the Palo Alto Networks Cortex XDR agent on Windows devices enables a user …

CVE-2025-0116

A Denial of Service (DoS) vulnerability in Palo Alto Networks PAN-OS software causes the firewall to unexpectedly reboot when processing …

CVE-2025-0128

A denial-of-service (DoS) vulnerability in the Simple Certificate Enrollment Protocol (SCEP) authentication feature of Palo Alto Networks PAN-OS® software enables …

CVE-2025-0129

An improper exception check in Palo Alto Networks Prisma Access Browser allows a low privileged user to prevent Prisma Access …

CVE-2026-73549