Is CVE-2026-73549 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-73549 being exploited in the wild.

How severe is CVE-2026-73549?

Medium severity, with a CVSS score of 5.3, published 21 September 2026.

Which products and versions are affected?

Envoy before 1.36.10, 1.37.x before 1.37.6, 1.38.x before 1.38.4, 1.39.x before 1.39.1.

Is there a fix for CVE-2026-73549?

A patch was published on 2026-09-21: Versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1 include the fix Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-73549 attacked?

It is attacked over the network, in a hosted service.

Am I affected by CVE-2026-73549?

Check whether you run Envoy at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-73549: Envoy scoped IPv6 address parsing denial of service

CVE-2026-73549 · Severity: medium · CVSS 5.3 · Published 2026-09-21

Envoy is a cloud-native proxy that routes network traffic for applications. In deployments using transparent proxying or QUIC connections with IPv6 scoped addresses, a malformed IPv6 address containing a scope identifier can crash the Envoy process, causing a service outage. This affects versions prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

Technologies: Envoy. Vendors: Envoy.

Quick answers

Is CVE-2026-73549 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-73549 being exploited in the wild.
How severe is CVE-2026-73549?: Medium severity, with a CVSS score of 5.3, published 21 September 2026.
Which products and versions are affected?: Envoy before 1.36.10, 1.37.x before 1.37.6, 1.38.x before 1.38.4, 1.39.x before 1.39.1.
Is there a fix for CVE-2026-73549?: A patch was published on 2026-09-21: Versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1 include the fix Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-73549 attacked?: It is attacked over the network, in a hosted service.
Am I affected by CVE-2026-73549?: Check whether you run Envoy at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability exists in Envoy's Utility::copyInternetAddressAndPort and QUIC client-address parsing code, which reconstructs scoped IPv6 addresses as strings including percent-encoded scope identifiers. When these strings are parsed with inet_pton, the parser cannot handle the scope identifier, triggering an exception or process abort. Exploitation requires either a kernel-provided original destination in transparent-proxy deployments or a malformed address via the QUIC connection path; HTTP requests using the use_http_header override filter out scoped addresses earlier and are not affected.

Affected products

Envoy Envoy before 1.36.10, 1.37.x before 1.37.6, 1.38.x before 1.38.4, 1.39.x before 1.39.1

Timeline

2026-09-21: disclosed
2026-09-21: patched: Versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1 include the fix

References

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