CVE-2019-9516 Some HTTP/2 implementations are vulnerable to a header leak, potentially leading to a denial of service
Attackers can cause denial of service by sending HTTP/2 headers with zero-length names and values, exhausting server memory.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2019-9516?
CVE-2019-9516 is a high-severity denial of service vulnerability in Apache Traffic Server, published on 13 Aug 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Some HTTP/2 implementations are vulnerable to a header leak, potentially leading to a denial of service. 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.
Which versions are affected by CVE-2019-9516?
It affects 19 products.
Products include Apache Traffic Server, Apple Swiftnio, Canonical Ubuntu Linux, Debian Debian Linux, F5 Nginx, Fedoraproject Fedora and 13 more.
How do I fix CVE-2019-9516?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2019-9516 being exploited?
There is no known exploitation of CVE-2019-9516 in the wild and no public exploit code.
Other vulnerabilities in Apache Traffic Server
Sources
Also known as ALPINE-CVE-2019-9516, CLEANSTART-2026-HE94703, CLEANSTART-2026-UM64475, DEBIAN-CVE-2019-9516, GHSA-6gw7-c226-vg73, UBUNTU-CVE-2019-9516.