CVE-2026-73548 Envoy - HTTP Request Smuggling

Envoy < 1.36.10, 1.37.6, 1.38.4, and 1.39.1 contains an HTTP request smuggling caused by improper handling of non-WebSocket HTTP upgrades, letting unauthenticated HTTP/2 clients smuggle requests and receive responses intended for others, exploit requires specific upgrade configurations.

CVSS base score 7.5 /10
High
CISA KEV
Not listed
Public exploit
Proof of concept available
EPSS
0.46% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
HTTP Request Smuggling
Impact
Information Disclosure
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Published
21 September 2026
Updated
15 October 2026
Weakness
CWE-444

Vendor fix

Update to versions 1.36.10, 1.37.6, 1.38.4, or 1.39.1 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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