CVE-2020-7694: Uvicorn Log Injection Vulnerability

HIGH
Advisory Identifier: GHSA-33c7-2mpw-hg34
Share
CVSS 7.5
CWE-116 CWE-94
Published
Advisory Summary

CVE-2020-7694 is a HIGH (CVSS 7.5) log injection vulnerability (CWE-116: Improper Encoding or Escaping of Output) affecting Uvicorn libraries in the PyPI ecosystem. The issue involves log injection in uvicorn. Remediation is available by upgrading affected packages to version 0.11.7.

CVE-2020-7694 at a Glance

CVE Identifier CVE-2020-7694
GHSA Identifier GHSA-33c7-2mpw-hg34
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-116: Improper Encoding or Escaping of Output
Affected Product Uvicorn
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.5

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:N/S:U/C:N/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2020-7694

To remediate this vulnerability, upgrade all affected Uvicorn dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

uvicorn fixed: 0.11.7 
pip install uvicorn>=0.11.7
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show uvicorn

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2020-7694, inspect your installed packages using pip:

pip show uvicorn

Analyze the terminal output to locate any version of Uvicorn in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.11.7), your application is affected.

Note: The pip show uvicorn command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-116: Improper Encoding or Escaping of Output, where the product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. as a result, the intended structure of the message is not preserved. In Uvicorn, 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

This affects all versions of package uvicorn. The request logger provided by the package is vulnerable to ASNI escape sequence injection. Whenever any HTTP request is received, the default behaviour of uvicorn is to log its details to either the console or a log file. When attackers request crafted URLs with percent-encoded escape sequences, the logging component will log the URL after it's been processed with urllib.parse.unquote, therefore converting any percent-encoded characters into their single-character equivalent, which can have special meaning in terminal emulators. By requesting URLs with crafted paths, attackers can: * Pollute uvicorn's access logs, therefore jeopardising the integrity of such files. * Use ANSI sequence codes to attempt to interact with the terminal emulator that's displaying the logs (either in real time or from a file).

CVE-2020-7694 Affected Uvicorn Versions

1 component(s)
Fixed Versions:
0.11.7
Product / Package Ecosystem Affected Versions Fixed Version
uvicorn
pypi/uvicorn
PyPI
< 0.11.7
0.11.7

References

NVD — CVE-2020-7694 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-7694
Uvicorn Source Repository REPOSITORY
https://github.com/encode/uvicorn/issues/723
Security Fix Commit FIX COMMIT
https://github.com/encode/uvicorn/commit/895807f94ea9a8e588605c12076b7d7517cda503
Uvicorn Source Repository REPOSITORY
https://github.com/encode/uvicorn
Uvicorn Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/uvicorn/PYSEC-2020-150.yaml
snyk.io/vuln/snyk-python-uv... WEB
https://snyk.io/vuln/SNYK-PYTHON-UVICORN-575560

Frequently Asked Questions

What is CVE-2020-7694?
CVE-2020-7694 is a security vulnerability in Uvicorn involving Log injection in uvicorn under CWE-116: Improper Encoding or Escaping of Output.
Which Uvicorn versions are affected?
Affected versions include releases prior to 0.11.7 across affected packages: uvicorn.
What version fixes CVE-2020-7694?
Upgrading to 0.11.7 (or the latest patched release for your respective branch) resolves the vulnerability.
Is uvicorn affected?
Yes, uvicorn is affected in releases prior to 0.11.7. Upgrade your dependency to 0.11.7 or later.
What is the CVSS score of CVE-2020-7694?
CVE-2020-7694 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
What CWE is associated with CVE-2020-7694?
CVE-2020-7694 is classified under CWE-116: Improper Encoding or Escaping of Output (The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.).
How can I check PyPI dependencies for CVE-2020-7694?
Run the dependency tree command: 'pip show uvicorn'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-33c7-2mpw-hg34",
  "modified" : "2024-11-18T22:32:53Z",
  "published" : "2020-07-29T18:07:16Z",
  "aliases" : [ "CVE-2020-7694" ],
  "summary" : "Log injection in uvicorn",
  "details" : "This affects all versions of package uvicorn. The request logger provided by the package is vulnerable to ASNI escape sequence injection. Whenever any HTTP request is received, the default behaviour of uvicorn is to log its details to either the console or a log file. When attackers request crafted URLs with percent-encoded escape sequences, the logging component will log the URL after it's been processed with urllib.parse.unquote, therefore converting any percent-encoded characters into their single-character equivalent, which can have special meaning in terminal emulators. By requesting URLs with crafted paths, attackers can: * Pollute uvicorn's access logs, therefore jeopardising the integrity of such files. * Use ANSI sequence codes to attempt to interact with the terminal emulator that's displaying the logs (either in real time or from a file).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "uvicorn"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.11.7"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-7694"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/encode/uvicorn/issues/723"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/encode/uvicorn/commit/895807f94ea9a8e588605c12076b7d7517cda503"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/encode/uvicorn"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/uvicorn/PYSEC-2020-150.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://snyk.io/vuln/SNYK-PYTHON-UVICORN-575560"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-116", "CWE-94" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2020-07-29T17:37:27Z",
    "nvd_published_at" : "2020-07-27T12:15:00Z"
  }
}