ASA-2019-00520 – nginx: Excessive memory usage in HTTP/2 with zero length headers

Posted on by Allele Security Intelligence in Alerts

Allele Security Alert

ASA-2019-00520

Identifier(s)

ASA-2019-00520, CVE-2019-9516

Title

Excessive memory usage in HTTP/2 with zero length headers

Vendor(s)

NGINX, Inc

Product(s)

nginx

Affected version(s)

nginx versions since 1.9.5 up to and including 1.17.2

Fixed version(s)

nginx version 1.17.3
nginx version 1.16.1

Proof of concept

Unknown

Description

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.

Technical details

The attacker sends a stream of headers with a 0-length header name and 0-length header value, optionally Huffman encoded into 1-byte or greater headers. Some implementations allocate memory for these headers and keep the allocation alive until the session dies. This can consume excess memory, potentially leading to a denial of service.

Credits

Jonathan Looney (Netflix)

Reference(s)

nginx security advisories
https://nginx.org/en/security_advisories.html

[nginx-announce] nginx security advisory (CVE-2019-9511, CVE-2019-9513, CVE-2019-9516)
https://mailman.nginx.org/pipermail/nginx-announce/2019/000249.html

HTTP/2 Denial of Service Advisory
https://github.com/Netflix/security-bulletins/blob/master/advisories/third-party/2019-002.md

Bug 1741864 (CVE-2019-9516) – CVE-2019-9516 HTTP/2: 0-length headers leads to denial of service [NEEDINFO]
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-9516

NGINX Updates Mitigate the August 2019 HTTP/2 Vulnerabilities
https://www.nginx.com/blog/nginx-updates-mitigate-august-2019-http-2-vulnerabilities/

HTTP/2: reject zero length headers with PROTOCOL_ERROR.
https://hg.nginx.org/nginx/rev/4f4b83f00cf1

CVE-2019-9516 - Red Hat Customer Portal
https://access.redhat.com/security/cve/CVE-2019-9516

CVE-2019-9516
https://security-tracker.debian.org/tracker/CVE-2019-9516

CVE-2019-9516 in Ubuntu
https://people.canonical.com/~ubuntu-security/cve/CVE-2019-9516.html

CVE-2019-9516 | SUSE
https://www.suse.com/security/cve/CVE-2019-9516

CVE-2019-9516
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-9516

CVE-2019-9516
https://nvd.nist.gov/vuln/detail/CVE-2019-9516

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Last modified: August 25, 2019

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