Allele Security Alert
Excessive CPU usage in HTTP/2 with small window updates
nginx versions since 1.9.5 up to and including 1.17.2
nginx version 1.17.3
nginx version 1.16.1
Proof of concept
Several security issues were identified in nginx HTTP/2 implementation, which might cause excessive memory consumption and CPU usage (CVE-2019-9511, CVE-2019-9513, CVE-2019-9516).
The issues affect nginx compiled with the ngx_http_v2_module (not compiled by default) if the “http2” option of the “listen” directive is used in a configuration file.
The attacker requests a large amount of data from a specified resource over multiple streams. They manipulate window size and stream priority to force the server to queue the data in 1-byte chunks. Depending on how efficiently this data is queued, this can consume excess CPU, memory, or both, potentially leading to a denial of service.
Jonathan Looney (Netflix)
nginx security advisories
[nginx-announce] nginx security advisory (CVE-2019-9511, CVE-2019-9513, CVE-2019-9516)
HTTP/2 Denial of Service Advisory
Bug 1741860 (CVE-2019-9511) – CVE-2019-9511 HTTP/2: large amount of data request leads to denial of service
HTTP/2: limited number of DATA frames.
NGINX Updates Mitigate the August 2019 HTTP/2 Vulnerabilities
CVE-2019-9511 - Red Hat Customer Portal
CVE-2019-9511 | SUSE
If there is any error in this alert or you wish a comprehensive analysis, let us know.
Last modified: October 2, 2019