CVE-2026-73512 Envoy: use-after-free in QUIC on internal redirects
An attacker can crash the Envoy proxy by sending HTTP/3 datagrams during internal redirects when Capsule Protocol is enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-73512?
CVE-2026-73512 is a high-severity use after free vulnerability in Envoyproxy Envoy, published on 21 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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 HttpDatagramHandler caches the current RequestDecoder when Capsule Protocol is enabled. Stream recreation, including an internal redirect, replaces the ActiveStream and updates EnvoyQuicServerStream but does not update the handler's cached pointer. A subsequent HTTP/3 datagram can call decodeData through the freed decoder, causing invalid virtual dispatch and a process crash. The relevant scope boundary is that hTTP/3 datagrams and Capsule Protocol must be enabled, and the request must enter a stream-recreation path such as an internal redirect. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.
Weakness: CWE-416
Which versions are affected by CVE-2026-73512?
1 open source package ship an affected version, including envoy. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
envoy Bitnami | All versions | 1.36.10, 1.37.6, 1.38.4, 1.39.1 |
Products include Envoyproxy Envoy.
How do I fix CVE-2026-73512?
Upgrade envoy to a fixed version for your release line: 1.36.10, 1.37.6, 1.38.4 or 1.39.1.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-73512 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73512 exists.
Other vulnerabilities in Envoyproxy Envoy
Sources
Also known as BIT-envoy-2026-73512, GHSA-r6j2-mrm5-72mg, MINI-923w-8g5r-5qw3, MINI-h8rh-gm8r-gjgc, MINI-hr6m-jmqh-q3xq, MINI-rxw4-3m3w-89cv.