CVE-2021-39155 Authorization Policy Bypass Due to Case Insensitive Host Comparison

2021-08-2422:25:18

CWE-178

GitHub_M

www.cve.org

8.3 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

LOW

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

8.4 High

AI Score

Confidence

High

0.001 Low

EPSS

Percentile

49.8%

JSON

Istio is an open source platform for providing a uniform way to integrate microservices, manage traffic flow across microservices, enforce policies and aggregate telemetry data. According to RFC 4343, Istio authorization policy should compare the hostname in the HTTP Host header in a case insensitive way, but currently the comparison is case sensitive. The proxy will route the request hostname in a case-insensitive way which means the authorization policy could be bypassed. As an example, the user may have an authorization policy that rejects request with hostname “httpbin.foo” for some source IPs, but the attacker can bypass this by sending the request with hostname “Httpbin.Foo”. Patches are available in Istio 1.11.1, Istio 1.10.4 and Istio 1.9.8. As a work around a Lua filter may be written to normalize Host header before the authorization check. This is similar to the Path normalization presented in the Security Best Practices guide.

CNA Affected

[
  {
    "product": "istio",
    "vendor": "istio",
    "versions": [
      {
        "status": "affected",
        "version": "<= 1.9.8"
      },
      {
        "status": "affected",
        "version": ">= 1.10.0, < 1.10.4"
      },
      {
        "status": "affected",
        "version": ">= 1.11.0, < 1.11.1"
      }
    ]
  }
]