8.6
HIGH
CVE-2021-32779
"Envoy Fragment Path Normalization Unauthorized Access Vulnerability"
Description

Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. In affected versions envoy incorrectly handled a URI '#fragment' element as part of the path element. Envoy is configured with an RBAC filter for authorization or similar mechanism with an explicit case of a final "/admin" path element, or is using a negative assertion with final path element of "/admin". The client sends request to "/app1/admin#foo". In Envoy prior to 1.18.0, or 1.18.0+ configured with path_normalization=false. Envoy treats fragment as a suffix of the query string when present, or as a suffix of the path when query string is absent, so it evaluates the final path element as "/admin#foo" and mismatches with the configured "/admin" path element. In Envoy 1.18.0+ configured with path_normalization=true. Envoy transforms this to /app1/admin%23foo and mismatches with the configured /admin prefix. The resulting URI is sent to the next server-agent with the offending "#foo" fragment which violates RFC3986 or with the nonsensical "%23foo" text appended. A specifically constructed request with URI containing '#fragment' element delivered by an untrusted client in the presence of path based request authorization resulting in escalation of Privileges when path based request authorization extensions. Envoy versions 1.19.1, 1.18.4, 1.17.4, 1.16.5 contain fixes that removes fragment from URI path in incoming requests.

INFO

Published Date :

Aug. 24, 2021, 9:15 p.m.

Last Modified :

Oct. 25, 2022, 3:56 p.m.

Source :

[email protected]

Remotely Exploitable :

Yes !

Impact Score :

4.0

Exploitability Score :

3.9
Affected Products

The following products are affected by CVE-2021-32779 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 Envoyproxy envoy
: 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-2021-32779.

URL Resource
https://github.com/envoyproxy/envoy/security/advisories/GHSA-r222-74fw-jqr9 Third Party Advisory
https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_history Vendor 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-2021-32779 vulnerability anywhere in the article.

The following table lists the changes that have been made to the CVE-2021-32779 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]

    Oct. 25, 2022

    Action Type Old Value New Value
    Removed CWE NIST CWE-863
    Added CWE NIST CWE-697
  • Reanalysis by [email protected]

    Jun. 15, 2022

    Action Type Old Value New Value
    Changed CPE Configuration OR *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.16.0 up to (excluding) 1.16.5 *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.17.0 up to (excluding) 1.17.4 *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.18.0 up to (excluding) 1.18.4 *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.19.0 up to (excluding) 1.91.1 OR *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.16.0 up to (excluding) 1.16.5 *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.17.0 up to (excluding) 1.17.4 *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.18.0 up to (excluding) 1.18.4 *cpe:2.3:a:envoyproxy:envoy:1.19.0:*:*:*:*:*:*:*
  • Reanalysis by [email protected]

    Sep. 07, 2021

    Action Type Old Value New Value
    Removed CVSS V3.1 NIST AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    Added CVSS V3.1 NIST AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
  • Initial Analysis by [email protected]

    Sep. 01, 2021

    Action Type Old Value New Value
    Added CVSS V2 NIST (AV:N/AC:L/Au:N/C:P/I:P/A:P)
    Added CVSS V3.1 NIST AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    Changed Reference Type https://github.com/envoyproxy/envoy/security/advisories/GHSA-r222-74fw-jqr9 No Types Assigned https://github.com/envoyproxy/envoy/security/advisories/GHSA-r222-74fw-jqr9 Third Party Advisory
    Changed Reference Type https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_history No Types Assigned https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_history Vendor Advisory
    Added CWE NIST CWE-863
    Added CPE Configuration OR *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.16.0 up to (excluding) 1.16.5 *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.17.0 up to (excluding) 1.17.4 *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.18.0 up to (excluding) 1.18.4 *cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* versions from (including) 1.19.0 up to (excluding) 1.91.1
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-2021-32779 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-2021-32779 weaknesses.

CAPEC-3: Using Leading 'Ghost' Character Sequences to Bypass Input Filters Using Leading 'Ghost' Character Sequences to Bypass Input Filters CAPEC-6: Argument Injection Argument Injection CAPEC-7: Blind SQL Injection Blind SQL Injection CAPEC-8: Buffer Overflow in an API Call Buffer Overflow in an API Call CAPEC-9: Buffer Overflow in Local Command-Line Utilities Buffer Overflow in Local Command-Line Utilities CAPEC-10: Buffer Overflow via Environment Variables Buffer Overflow via Environment Variables CAPEC-14: Client-side Injection-induced Buffer Overflow Client-side Injection-induced Buffer Overflow CAPEC-15: Command Delimiters Command Delimiters CAPEC-24: Filter Failure through Buffer Overflow Filter Failure through Buffer Overflow CAPEC-41: Using Meta-characters in E-mail Headers to Inject Malicious Payloads Using Meta-characters in E-mail Headers to Inject Malicious Payloads CAPEC-43: Exploiting Multiple Input Interpretation Layers Exploiting Multiple Input Interpretation Layers CAPEC-44: Overflow Binary Resource File Overflow Binary Resource File CAPEC-45: Buffer Overflow via Symbolic Links Buffer Overflow via Symbolic Links CAPEC-46: Overflow Variables and Tags Overflow Variables and Tags CAPEC-47: Buffer Overflow via Parameter Expansion Buffer Overflow via Parameter Expansion CAPEC-52: Embedding NULL Bytes Embedding NULL Bytes CAPEC-53: Postfix, Null Terminate, and Backslash Postfix, Null Terminate, and Backslash CAPEC-64: Using Slashes and URL Encoding Combined to Bypass Validation Logic Using Slashes and URL Encoding Combined to Bypass Validation Logic CAPEC-67: String Format Overflow in syslog() String Format Overflow in syslog() CAPEC-71: Using Unicode Encoding to Bypass Validation Logic Using Unicode Encoding to Bypass Validation Logic CAPEC-73: User-Controlled Filename User-Controlled Filename CAPEC-78: Using Escaped Slashes in Alternate Encoding Using Escaped Slashes in Alternate Encoding CAPEC-79: Using Slashes in Alternate Encoding Using Slashes in Alternate Encoding CAPEC-80: Using UTF-8 Encoding to Bypass Validation Logic Using UTF-8 Encoding to Bypass Validation Logic CAPEC-88: OS Command Injection OS Command Injection CAPEC-92: Forced Integer Overflow Forced Integer Overflow CAPEC-120: Double Encoding Double Encoding CAPEC-182: Flash Injection Flash Injection CAPEC-267: Leverage Alternate Encoding Leverage Alternate Encoding
Exploit Prediction

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

0.10 }} 0.01%

score

0.42031

percentile

CVSS31 - Vulnerability Scoring System
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality
Integrity
Availability
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