Envoy Proxy up to 1.36.9/1.37.5/1.38.3/1.39.0 confused deputy

Summaryinfo

A vulnerability was found in Envoy Proxy Envoy up to 1.36.9/1.37.5/1.38.3/1.39.0. It has been rated as problematic. Affected by this issue is some unknown functionality. The manipulation leads to confused deputy. This vulnerability is listed as CVE-2026-73548. The attack may be initiated remotely. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Envoy Proxy Envoy up to 1.36.9/1.37.5/1.38.3/1.39.0. This issue affects an unknown function. The manipulation with an unknown input leads to a confused deputy vulnerability. Using CWE to declare the problem leads to CWE-441. The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere. This causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor. Impacted is confidentiality. The summary by CVE is:

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 forwards data for a configured non-WebSocket HTTP upgrade before the upstream accepts the upgrade. An unauthenticated HTTP/2 client can place a complete HTTP/1.1 request in extended CONNECT data; Envoy downgrades the request, writes the data unframed to a keep-alive HTTP/1.1 upstream, and returns the socket to the shared pool while the smuggled response remains queued. A different downstream client can then receive the attacker's response. The relevant scope boundary is that webSocket upgrades, plain CONNECT, disabled backend keep-alive, per-downstream pools, and max_requests_per_connection set to 1 are not affected by the demonstrated path. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-73548 since 08/12/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available.

Upgrading to version 1.36.10, 1.37.6, 1.38.4 or 1.39.1 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Firewall Software

Vendor

• Envoy Proxy

Name

• Envoy

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19
• 1.20
• 1.21
• 1.22
• 1.23
• 1.24
• 1.25
• 1.26
• 1.27
• 1.28
• 1.29
• 1.30
• 1.31
• 1.32
• 1.33
• 1.34
• 1.35
• 1.36
• 1.36.0
• 1.36.1
• 1.36.2
• 1.36.3
• 1.36.4
• 1.36.5
• 1.36.6
• 1.36.7
• 1.36.8
• 1.36.9
• 1.37
• 1.37.0
• 1.37.1
• 1.37.2
• 1.37.3
• 1.37.4
• 1.37.5
• 1.38
• 1.38.0
• 1.38.1
• 1.38.2
• 1.38.3
• 1.39.0

License

• free

CPE 2.3info

• 🔒
• 🔒
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CPE 2.2info

• 🔒
• 🔒
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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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