CVE-2023-27491

Name: CVE-2023-27491
Creator: NVD / NIST
Published: 2023-04-04T19:15:07.15+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.1/10EPSS 0.87%

Last modified Jun 17, 2026

CVE-2023-27491 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. Envoy is an open source edge and service proxy designed for cloud-native applications. Compliant HTTP/1 service should reject malformed request lines. EPSS estimates a 0.87% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

9.1/10

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

EPSS Probability

0.87%

54.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Envoyproxy	Envoy	< 1.22.9
Envoyproxy	Envoy	>= 1.23.0, < 1.23.6
Envoyproxy	Envoy	>= 1.24.0, < 1.24.4
Envoyproxy	Envoy	>= 1.25.0, < 1.25.3

References

https://datatracker.ietf.org/doc/html/rfc9113#section-8.3Not Applicable
https://datatracker.ietf.org/doc/html/rfc9114#section-4.3.1Not Applicable
https://github.com/envoyproxy/envoy/security/advisories/GHSA-5jmv-cw9p-f9rpExploit, Vendor Advisory
https://www.rfc-editor.org/rfc/rfc9110#section-5.6.2Not Applicable
https://datatracker.ietf.org/doc/html/rfc9113#section-8.3Not Applicable
https://datatracker.ietf.org/doc/html/rfc9114#section-4.3.1Not Applicable
https://github.com/envoyproxy/envoy/security/advisories/GHSA-5jmv-cw9p-f9rpExploit, Vendor Advisory
https://www.rfc-editor.org/rfc/rfc9110#section-5.6.2Not Applicable

Timeline

Published: Apr 4, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-27491?

How severe is CVE-2023-27491?

CVE-2023-27491 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 0.87% probability of exploitation in the next 30 days.

How do I fix CVE-2023-27491?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2023-27491?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST