CVE-2023-35943: Envoy vulnerable to CORS filter segfault when origin header is removed

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2023-07-25 · updated 2026-06-17
Weakness: CWE-416

Description

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.27.0, 1.26.4, 1.25.9, 1.24.10, and 1.23.12, the CORS filter will segfault and crash Envoy when the `origin` header is removed and deleted between `decodeHeaders`and `encodeHeaders`. Versions 1.27.0, 1.26.4, 1.25.9, 1.24.10, and 1.23.12 have a fix for this issue. As a workaround, do not remove the `origin` header in the Envoy configuration.

Affected products

envoyproxy envoy: from 1.23.0 before 1.23.12; from 1.24.0 before 1.24.10; from 1.25.0 before 1.25.9; from 1.26.0 before 1.26.4 — fixed in 1.23.12, 1.24.10, 1.25.9, 1.26.4

How to fix

Upgrade to a fixed version: envoyproxy envoy 1.23.12, 1.24.10, 1.25.9, 1.26.4. Check the vendor advisory for mitigations.

References

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