CVE-2019-9517
Description
A vulnerability was found in HTTP/2. An attacker can open a HTTP/2 window so the peer can send without constraint. The TCP window remains closed so the peer cannot write the bytes on the wire. The attacker then sends a stream of requests for a large response object. Depending on how the server's queue is setup, the responses can consume excess memory, CPU, or both, potentially leading to a denial of service. The highest threat from this vulnerability is to system availability.
Statement
The package httpd versions as shipped with Red Hat Enterprise Linux 5, 6 and 7 are not affected by this issue as HTTP/2 support is not provided. This flaw has no available mitigation for nodejs package. It will be updated once the available fixes are released for Red Hat Enterprise Linux and Red Hat Software Collections.
The nodejs RPM shipped in OpenShift Container Platform 3.9 and 3.10 is not affected by this flaw as it does not contain the vulnerable code.
Mitigation
The httpd version shipped with Red Hat Enterprise Linux 8 provides HTTP/2 support through mod_http2 package. While mod_http2 package is not updated, users can disable HTTP/2 support as mitigation action by executing the following steps:
1. Stop httpd service:
$ systemctl stop httpd
2. Remove http/2 protocol support from configuration files:
$ sed -i 's/\(h2\)\|\(h2c\)//g' <httpd_config_file>
3. Validate configuration files to make sure all syntax is valid:
$ apachectl configtest
4. Restart httpd service:
$ systemctl start httpd
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 | 7.5 | 7.5 | 7.5 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | None | None | None |
| Integrity Impact | None | None | None |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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