8.3
HIGH
CVE-2021-39155
Istio Case-Insensitive HTTP Host Header Normalization 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.

INFO

Published Date :

Aug. 24, 2021, 11:15 p.m.

Last Modified :

Feb. 21, 2024, 9:01 p.m.

Source :

[email protected]

Remotely Exploitable :

Yes !

Impact Score :

5.5

Exploitability Score :

2.8
Affected Products

The following products are affected by CVE-2021-39155 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Istio istio
: Total Affected Vendor : 1 | Products : 1
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2021-39155.

URL Resource
https://datatracker.ietf.org/doc/html/rfc4343 Third Party Advisory
https://github.com/istio/istio/security/advisories/GHSA-7774-7vr3-cc8j Third Party Advisory

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2021-39155 vulnerability anywhere in the article.

The following table lists the changes that have been made to the CVE-2021-39155 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • CVE Modified by [email protected]

    May. 14, 2024

    Action Type Old Value New Value
  • Reanalysis by [email protected]

    Feb. 21, 2024

    Action Type Old Value New Value
    Added CWE NIST CWE-863
  • Initial Analysis by [email protected]

    Aug. 31, 2021

    Action Type Old Value New Value
    Added CVSS V2 NIST (AV:N/AC:L/Au:N/C:P/I:N/A:N)
    Added CVSS V3.1 NIST AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
    Changed Reference Type https://datatracker.ietf.org/doc/html/rfc4343 No Types Assigned https://datatracker.ietf.org/doc/html/rfc4343 Third Party Advisory
    Changed Reference Type https://github.com/istio/istio/security/advisories/GHSA-7774-7vr3-cc8j No Types Assigned https://github.com/istio/istio/security/advisories/GHSA-7774-7vr3-cc8j Third Party Advisory
    Added CWE NIST CWE-178
    Added CPE Configuration OR *cpe:2.3:a:istio:istio:*:*:*:*:*:*:*:* versions up to (excluding) 1.9.8 *cpe:2.3:a:istio:istio:*:*:*:*:*:*:*:* versions from (including) 1.10.0 up to (excluding) 1.10.4 *cpe:2.3:a:istio:istio:*:*:*:*:*:*:*:* versions from (including) 1.11.0 up to (excluding) 1.11.1
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2021-39155 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2021-39155 weaknesses.

Exploit Prediction

EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days.

0.14 }} 0.01%

score

0.49378

percentile

CVSS31 - Vulnerability Scoring System
Attack Vector
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