CVE-2023-27491 - CVE House
Back to Database
Status published Medium CVE-2023-27491

Envoy forwards invalid Http2/Http3 downstream headers

Vulnerability Description

Envoy is an open source edge and service proxy designed for cloud-native applications. Compliant HTTP/1 service should reject malformed request lines. Prior to versions 1.26.0, 1.25.3, 1.24.4, 1.23.6, and 1.22.9, There is a possibility that non compliant HTTP/1 service may allow malformed requests, potentially leading to a bypass of security policies. This issue is fixed in versions 1.26.0, 1.25.3, 1.24.4, 1.23.6, and 1.22.9.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

THREAT MONITOR

Am I Vulnerable?

Launch our assessment wizard to check if your infrastructure is exposed to • CVE-2023-27491

Credits & Attribution

No credits recorded in the NVD database.

References

More from envoyproxy

View All →
CVE-2025-66220
Envoy’s TLS certificate matcher for `match_typed_subject_alt_names` may incorrectly treat certificates containing an embedded null byte
Medium 5
CVE-2025-64763
Envoy forwards early CONNECT data in TCP proxy mode
Low 3.7
CVE-2025-64527
Envoy crashes when JWT authentication is configured with the remote JWKS fetching
Medium 6.5
CVE-2025-62504
Envoy Lua filter use-after-free when oversized rewritten response body causes crash
Medium 6.5
CVE-2025-62409
Envoy allows large requests and responses to cause TCP connection pool crash
Medium 6.6

Affected Vendor

Affected Software

envoy
Vulnerable Versions:
>= 1.25.0, < 1.25.3, >= 1.24.0, < 1.24.4, >= 1.23.0, < 1.23.6, < 1.22.9

Timeline

Official Publish: April 4th, 2023
Last Modified: February 11th, 2025
Added to House: July 22nd, 2026

CVSS Vectors

V3: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

Weaknesses (CWE)

CWE-20

MITRE ATT&CK TTPs

T1190 Exploit Public-Facing Application
Initial Access
T1059 Command and Scripting Interpreter
Execution
T1068 Exploitation for Privilege Escalation
Privilege Escalation
T1213 Data from Information Repositories
Collection
T1565.002 Stored Data Manipulation
Impact