CVE-2021-39155: Istio.io/istio Authorization Policy Bypass Due To Vulnerability
HIGHCVE-2021-39155 is a HIGH (CVSS 8.3) authorization policy bypass due to vulnerability (CWE-178: Improper Handling of Case Sensitivity) affecting Istio.io/istio libraries in the Go ecosystem. The issue involves authorization policy bypass due to case insensitive host comparison. Remediation is available by upgrading affected packages to version 1.9.8, 1.10.4, 1.11.1.
CVE-2021-39155 at a Glance
Security Impact
CVSS: 8.3
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L).
How to Fix CVE-2021-39155
To remediate this vulnerability, upgrade all affected Istio.io/istio dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade istio.io/istio to 1.9.8Upgrade istio.io/istio to 1.10.4Upgrade istio.io/istio to 1.11.1Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for istio.io/istioHow to Check if You Are Affected
To determine whether your application is affected by CVE-2021-39155, inspect your project dependencies for Istio.io/istio:
inspect dependencies for istio.io/istioAnalyze the terminal output to locate any version of Istio.io/istio in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.9.8), your application is affected.
Note: Verify declared build manifests and deployed runtime container environments.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-178: Improper Handling of Case Sensitivity, where the product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results. In Istio.io/istio, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2021-39155 Affected Istio.io/istio Versions
3 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
istio.io/istio
|
Go |
< 1.9.8
|
1.9.8
|
|
istio.io/istio
|
Go |
≥ 1.10.0
< 1.10.4
|
1.10.4
|
|
istio.io/istio
|
Go |
≥ 1.11.0
< 1.11.1
All 1 versions
1.11.0
|
1.11.1
|
References
Frequently Asked Questions
What is CVE-2021-39155?
Which Istio.io/istio versions are affected?
What version fixes CVE-2021-39155?
Is istio.io/istio affected?
What is the CVSS score of CVE-2021-39155?
What CWE is associated with CVE-2021-39155?
How can I check Go dependencies for CVE-2021-39155?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-7774-7vr3-cc8j",
"modified" : "2021-12-13T13:09:54Z",
"published" : "2021-08-30T16:15:56Z",
"aliases" : [ "CVE-2021-39155" ],
"summary" : "Authorization Policy Bypass Due to Case Insensitive Host Comparison",
"details" : "### Impact\nAccording 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 Envoy proxy will route the request hostname in a case-insensitive way which means the authorization policy could be bypassed.\n \nAs 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\".\n\n### Patches\n* Istio 1.11.1 and above\n* Istio 1.10.4 and above\n* Istio 1.9.8 and above\n\n### Workarounds\nA 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.\n\n### References\nMore details can be found in the [Istio Security Bulletin](https://istio.io/latest/news/security/istio-security-2021-008).\n\n### For more information\nIf you have any questions or comments about this advisory, please email us at istio-security-vulnerability-reports@googlegroups.com\n",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "istio.io/istio"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "1.9.8"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "istio.io/istio"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "1.10.0"
}, {
"fixed" : "1.10.4"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "istio.io/istio"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "1.11.0"
}, {
"fixed" : "1.11.1"
} ]
} ],
"versions" : [ "1.11.0" ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/istio/istio/security/advisories/GHSA-7774-7vr3-cc8j"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-39155"
}, {
"type" : "WEB",
"url" : "https://github.com/istio/istio/commit/084b417a486dbe9b9024d4812877016a484572b1"
}, {
"type" : "WEB",
"url" : "https://github.com/istio/istio/commit/76ed51413ddd2a7fa253a368ab20a9cec5fb1cbe"
}, {
"type" : "WEB",
"url" : "https://github.com/istio/istio/commit/90b00bdf891e6c770cb3235c14a9b1fda96cc7c5"
}, {
"type" : "WEB",
"url" : "https://datatracker.ietf.org/doc/html/rfc4343"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/istio/istio"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-178" ],
"severity" : "HIGH",
"github_reviewed" : true,
"github_reviewed_at" : "2021-08-25T22:29:16Z",
"nvd_published_at" : "2021-08-24T23:15:00Z"
}
}