CVE-2019-16789: HTTP Request Smuggling in Waitress Invalid Whitespace Characters Vulnerability

MODERATE
Advisory Identifier: GHSA-968f-66r5-5v74
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CVSS 7.1
CWE-444
Published
Advisory Summary

CVE-2019-16789 is a MODERATE (CVSS 7.1) invalid whitespace characters vulnerability (CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')) affecting HTTP Request Smuggling in Waitress libraries in the PyPI ecosystem. The issue involves invalid whitespace characters in headers (follow-up). Remediation is available by upgrading affected packages to version 1.4.2.

CVE-2019-16789 at a Glance

CVE Identifier CVE-2019-16789
GHSA Identifier GHSA-968f-66r5-5v74
Severity MODERATE
CVSS v3.1 Base Score 7.1
CWE Classification CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Affected Product HTTP Request Smuggling in Waitress
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:H/A:N).

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

How to Fix CVE-2019-16789

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

waitress fixed: 1.4.2 
pip install waitress>=1.4.2
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 waitress

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2019-16789, inspect your installed packages using pip:

pip show waitress

Analyze the terminal output to locate any version of HTTP Request Smuggling in Waitress in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.4.2), your application is affected.

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

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling'), where the product acts as an intermediary http agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed http requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination. In HTTP Request Smuggling in Waitress, 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

### Impact The patches introduced to fix https://github.com/Pylons/waitress/security/advisories/GHSA-m5ff-3wj3-8ph4 were not complete and still would allow an attacker to smuggle requests/split a HTTP request with invalid data. This updates the existing CVE with ID: CVE-2019-16789 ### Patches Waitress version 1.4.2 has been updated to now validate HTTP headers better to avoid the issue, completely fixing all known issues with whitespace. ### Workarounds There are no work-arounds, upgrading to Waitress 1.4.2 is highly recommended. ### References See https://github.com/Pylons/waitress/security/advisories/GHSA-m5ff-3wj3-8ph4 for more information on the security issue. ### For more information If you have any questions or comments about this advisory: * open an issue at https://github.com/Pylons/waitress/issues (if not sensitive or security related) * email the Pylons Security mailing list: pylons-project-security@googlegroups.com (if security related)

CVE-2019-16789 Affected HTTP Request Smuggling in Waitress Versions

1 component(s)
Fixed Versions:
1.4.2
Product / Package Ecosystem Affected Versions Fixed Version
waitress
pypi/waitress
PyPI
< 1.4.2
1.4.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/Pylons/waitress/security/advisories/GHSA-968f-66r5-5v74
NVD — CVE-2019-16789 NVD
https://nvd.nist.gov/vuln/detail/CVE-2019-16789
HTTP Request Smuggling in Waitress Source Repository REPOSITORY
https://github.com/github/advisory-review/pull/14604
Security Fix Commit FIX COMMIT
https://github.com/Pylons/waitress/commit/11d9e138125ad46e951027184b13242a3c1de017
Security Fix Commit FIX COMMIT
https://github.com/Pylons/waitress/commit/ddb65b489d01d696afa1695b75fdd5df3e4ffdf8
access.redhat.com/errata/rhsa-2020:07... WEB
https://access.redhat.com/errata/RHSA-2020:0720
docs.pylonsproject.org/projects/waitress/e... WEB
https://docs.pylonsproject.org/projects/waitress/en/latest/#security-fixes
HTTP Request Smuggling in Waitress Source Repository REPOSITORY
https://github.com/Pylons/waitress
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-968f-66r5-5v74
HTTP Request Smuggling in Waitress Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/waitress/PYSEC-2019-138.yaml
lists.debian.org/debian-lts-announce... WEB
https://lists.debian.org/debian-lts-announce/2022/05/msg00011.html
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/GVDHR2DNKCNQ7YQXISJ45NT4IQDX3LJ7
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/LYEOTGWJZVKPRXX2HBNVIYWCX73QYPM5
HTTP Request Smuggling in Waitress Security Information SECURITY
https://www.oracle.com/security-alerts/cpuapr2022.html

Frequently Asked Questions

What is CVE-2019-16789?
CVE-2019-16789 is a security vulnerability in HTTP Request Smuggling in Waitress involving Invalid whitespace characters in headers (Follow-up) under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling').
Which HTTP Request Smuggling in Waitress versions are affected?
Affected versions include releases prior to 1.4.2 across affected packages: waitress.
What version fixes CVE-2019-16789?
Upgrading to 1.4.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is waitress affected?
Yes, waitress is affected in releases prior to 1.4.2. Upgrade your dependency to 1.4.2 or later.
What is the CVSS score of CVE-2019-16789?
CVE-2019-16789 has a CVSS v3.1 base score of 7.1 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:H/A:N.
What CWE is associated with CVE-2019-16789?
CVE-2019-16789 is classified under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') (The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.).
How can I check PyPI dependencies for CVE-2019-16789?
Run the dependency tree command: 'pip show waitress'. 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-968f-66r5-5v74",
  "modified" : "2024-11-19T13:58:27Z",
  "published" : "2020-01-06T18:44:21Z",
  "aliases" : [ "CVE-2019-16789" ],
  "summary" : "HTTP Request Smuggling in Waitress: Invalid whitespace characters in headers (Follow-up)",
  "details" : "### Impact\n\nThe patches introduced to fix https://github.com/Pylons/waitress/security/advisories/GHSA-m5ff-3wj3-8ph4 were not complete and still would allow an attacker to smuggle requests/split a HTTP request with invalid data.\n\nThis updates the existing CVE with ID: CVE-2019-16789\n\n### Patches\n\nWaitress version 1.4.2 has been updated to now validate HTTP headers better to avoid the issue, completely fixing all known issues with whitespace.\n\n### Workarounds\n\nThere are no work-arounds, upgrading to Waitress 1.4.2 is highly recommended.\n\n### References\n\nSee https://github.com/Pylons/waitress/security/advisories/GHSA-m5ff-3wj3-8ph4 for more information on the security issue.\n\n### For more information\n\nIf you have any questions or comments about this advisory:\n\n* open an issue at https://github.com/Pylons/waitress/issues (if not sensitive or security related)\n* email the Pylons Security mailing list: pylons-project-security@googlegroups.com (if security related)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:H/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:H/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "waitress"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.4.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/Pylons/waitress/security/advisories/GHSA-968f-66r5-5v74"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2019-16789"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/github/advisory-review/pull/14604"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/Pylons/waitress/commit/11d9e138125ad46e951027184b13242a3c1de017"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/Pylons/waitress/commit/ddb65b489d01d696afa1695b75fdd5df3e4ffdf8"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2020:0720"
  }, {
    "type" : "WEB",
    "url" : "https://docs.pylonsproject.org/projects/waitress/en/latest/#security-fixes"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/Pylons/waitress"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-968f-66r5-5v74"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/waitress/PYSEC-2019-138.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://lists.debian.org/debian-lts-announce/2022/05/msg00011.html"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/GVDHR2DNKCNQ7YQXISJ45NT4IQDX3LJ7"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/LYEOTGWJZVKPRXX2HBNVIYWCX73QYPM5"
  }, {
    "type" : "WEB",
    "url" : "https://www.oracle.com/security-alerts/cpuapr2022.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-444" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2020-01-06T18:43:11Z",
    "nvd_published_at" : "2019-12-26T17:15:00Z"
  }
}