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CVE-2026-73550

Envoyproxy Envoy vulnerability

7.5 HIGHPublic exploitEPSS 0.55%
  1. Published21 Sept 2026

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 copies every decoded HTTP/2 Host header value before discarding it when :authority is already present. The discarded value bypasses saveHeader, so its bytes and count are not charged against request header limits. An unauthenticated client can use HPACK indexing to submit many references to a large Host value across a bounded number of streams, forcing extreme header-copy allocation and causing the proxy to be out-of-memory killed. The relevant scope boundary is that the demonstrated amplification uses HTTP/2 HPACK and the duplicate Host discard behavior. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Envoyproxy Envoy≥ 1.37.0 < 1.37.6 · ≥ 1.38.0 < 1.38.4 · ≥ 1.39.0 < 1.39.1 · < 1.36.10

Remediation

Fixed in
Envoyproxy Envoy≥ 1.37.6

References

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Frequently asked

Is CVE-2026-73550 being actively exploited?

CVE-2026-73550 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.55%.

How severe is CVE-2026-73550?

CVE-2026-73550 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.55% probability of exploitation.

Which products are affected by CVE-2026-73550?

Affected products include Envoyproxy Envoy.

How do I fix CVE-2026-73550?

Upgrade affected software to a fixed version, for example Envoyproxy Envoy 1.37.6 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-73550 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.