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

Quick assessment

Affected
istio istio
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Istio是一套连接、管理和保护微服务的开放平台。 Istio 中存在安全漏洞，该漏洞允许攻击者绕过在规则中使用主机的Istio授权策略，从而可能获得对下游服务的访问权。

CVSS 8.3 · High EPSS 1.19% · P65
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I. Basic Information for CVE-2021-39155

Vulnerability Information
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Vulnerability Title
Authorization Policy Bypass Due to Case Insensitive Host Comparison
Source: CVE Program / CVE List V5
Vulnerability Description
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](https://datatracker.ietf.org/doc/html/rfc4343), 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](https://istio.io/latest/docs/ops/best-practices/security/#case-normalization) guide.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
大小写敏感处理不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Istio 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Istio是一套连接、管理和保护微服务的开放平台。 Istio 中存在安全漏洞，该漏洞允许攻击者绕过在规则中使用主机的Istio授权策略，从而可能获得对下游服务的访问权。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
istio istio <= 1.9.8 -

II. Public POCs for CVE-2021-39155

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III. Intelligence Information for CVE-2021-39155

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Vendor Advisories for CVE-2021-39155 (1)

Other References for CVE-2021-39155 (1)

IV. Related Vulnerabilities

Same product: istio
Same vendor: istio
Same weakness: CWE-178

V. Comments for CVE-2021-39155

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