Quick answers
- Is CVE-2026-73550 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-73550 being exploited in the wild.
- How severe is CVE-2026-73550?
- High severity, with a CVSS score of 7.5, published 21 September 2026.
- Which products and versions are affected?
- Envoy Prior to 1.36.10, 1.37.0 through 1.37.5, 1.38.0 through 1.38.3, 1.39.0.
- Is there a fix for CVE-2026-73550?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-73550 attacked?
- It is attacked over the network, in a hosted service.
- Am I affected by CVE-2026-73550?
- 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 is a denial-of-service in HTTP/2 header processing where dropped Host headers (when :authority is present) are not charged against request header limits. An attacker can use HPACK indexing to reference a large Host header value repeatedly across multiple streams, causing unbounded memory allocation that leads to out-of-memory conditions. The fix requires versions 1.36.10, 1.37.6, 1.38.4, or 1.39.1 which properly account for dropped header sizes in limit checks.
Affected products
- Envoy Envoy Prior to 1.36.10, 1.37.0 through 1.37.5, 1.38.0 through 1.38.3, 1.39.0
Timeline
- 2026-09-21: disclosed