CVE-2020-5236 Catastrophic backtracking in regex allows Denial of Service in Waitress

2020-02-0403:05:14

CWE-400

GitHub_M

www.cve.org

CVSS3

5.7

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

NONE

Availability Impact

HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

EPSS

0.001

Percentile

32.8%

JSON

Waitress version 1.4.2 allows a DOS attack When waitress receives a header that contains invalid characters. When a header like “Bad-header: xxxxxxxxxxxxxxx\x10” is received, it will cause the regular expression engine to catastrophically backtrack causing the process to use 100% CPU time and blocking any other interactions. This allows an attacker to send a single request with an invalid header and take the service offline. This issue was introduced in version 1.4.2 when the regular expression was updated to attempt to match the behaviour required by errata associated with RFC7230. The regular expression that is used to validate incoming headers has been updated in version 1.4.3, it is recommended that people upgrade to the new version of Waitress as soon as possible.

CNA Affected

[
  {
    "product": "Waitress",
    "vendor": "Pylons",
    "versions": [
      {
        "status": "affected",
        "version": "= 1.4.2"
      }
    ]
  }
]