// For flags

CVE-2023-35944

Envoy vulnerable to incorrect handling of HTTP requests and responses with mixed case schemes

Severity Score

5.3
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

1
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

Attend
*SSVC
Descriptions

Envoy is an open source edge and service proxy designed for cloud-native applications. Envoy allows mixed-case schemes in HTTP/2, however, some internal scheme checks are case-sensitive. Prior to versions 1.27.0, 1.26.4, 1.25.9, 1.24.10, and 1.23.12, this can lead to the rejection of requests with mixed-case schemes such as `htTp` or `htTps`, or the bypassing of some requests such as `https` in unencrypted connections. With a fix in versions 1.27.0, 1.26.4, 1.25.9, 1.24.10, and 1.23.12, Envoy will now lowercase scheme values by default, and change the internal scheme checks that were case-sensitive to be case-insensitive. There are no known workarounds for this issue.

A flaw was found in Envoy that allows for mixed-case schemes in HTTP/2. However, some internal scheme checks in Envoy are case-sensitive, leading to incorrect handling of requests and responses with mixed case schemes. For example, if a request with a mixed scheme HTTP is sent to the OAuth2 filter, it will fail the exact-match checks for HTTP and inform the remote endpoint the scheme is HTTP, thus potentially bypassing OAuth2 checks specific to HTTP requests.

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
None
* Common Vulnerability Scoring System
SSVC
  • Decision:Attend
Exploitation
Poc
Automatable
No
Tech. Impact
Total
* Organization's Worst-case Scenario
Timeline
  • 2023-06-20 CVE Reserved
  • 2023-07-25 CVE Published
  • 2024-07-31 EPSS Updated
  • 2024-10-23 CVE Updated
  • 2024-10-23 First Exploit
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
CWE
  • CWE-20: Improper Input Validation
  • CWE-178: Improper Handling of Case Sensitivity
  • CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Envoyproxy
Search vendor "Envoyproxy"
 Envoy
Search vendor "Envoyproxy" for product "Envoy"
 >= 1.23.0 < 1.23.12
Search vendor "Envoyproxy" for product "Envoy" and version " >= 1.23.0 < 1.23.12"
-
Affected
Envoyproxy
Search vendor "Envoyproxy"
 Envoy
Search vendor "Envoyproxy" for product "Envoy"
 >= 1.24.0 < 1.24.10
Search vendor "Envoyproxy" for product "Envoy" and version " >= 1.24.0 < 1.24.10"
-
Affected
Envoyproxy
Search vendor "Envoyproxy"
 Envoy
Search vendor "Envoyproxy" for product "Envoy"
 >= 1.25.0 < 1.25.9
Search vendor "Envoyproxy" for product "Envoy" and version " >= 1.25.0 < 1.25.9"
-
Affected
Envoyproxy
Search vendor "Envoyproxy"
 Envoy
Search vendor "Envoyproxy" for product "Envoy"
 >= 1.26.0 < 1.26.4
Search vendor "Envoyproxy" for product "Envoy" and version " >= 1.26.0 < 1.26.4"
-
Affected