CVE-2019-16786
Description
An HTTP-interpretation flaw was found in waitress which did not properly validate incoming HTTP headers. When parsing the Transfer-Encoding header, waitress would look only for a single string value. According to the HTTP standard, Transfer-Encoding should be a comma-separated list, with the inner-most encoding first, followed by any further transfer codings, ending with 'chunked'. Because of this flaw, requests sent with: "Transfer-Encoding: gzip, chunked" would get ignored, and waitress would use the Content-Length header instead to determine the body size of the HTTP message. A remote attacker could exploit this flaw to force waitress to accept potentially bad HTTP requests or treat a single request as multiple requests in the case of HTTP pipelining.
Statement
All affected Red Hat products ship but do not use the flawed version of python-waitress. The impact for these products is therefore rated as having a security impact of Low.
In Red Hat OpenStack Platform 13, because the flawed code is not used and the fix would require a substantial amount of development, no update will be provided at this time for the RHOSP13 python-waitress package.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.1 | 7.5 | 7.1 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | Low | High |
| Privileges Required | Low | None | Low |
| User Interaction | None | None | None |
| Scope | Changed | Unchanged | Changed |
| Confidentiality | High | None | High |
| Integrity Impact | Low | High | Low |
| Availability Impact | None | None | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N
Understanding the Weakness (CWE)
Integrity,Non-Repudiation,Access Control
Technical Impact: Unexpected State; Hide Activities; Bypass Protection Mechanism
An attacker could create HTTP messages to exploit a number of weaknesses including 1) the message can trick the web server to associate a URL with another URL's webpage and caching the contents of the webpage (web cache poisoning attack), 2) the message can be structured to bypass the firewall protection mechanisms and gain unauthorized access to a web application, and 3) the message can invoke a script or a page that returns client credentials (similar to a Cross Site Scripting attack).
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