FreeBSD VuXML: Documenting security issues in FreeBSD and the FreeBSD Ports Collection

h2o -- uninitialised memory access in HTTP3

Affected packages
h2o-devel < 2.3.0.d.20220131


VuXML ID 1d3677a8-9143-42d8-84a3-0585644dff4b
Discovery 2021-01-31
Entry 2022-02-02

Emil Lerner reports:

When receiving QUIC frames in certain order, HTTP/3 server-side implementation of h2o can be misguided to treat uninitialized memory as HTTP/3 frames that have been received. When h2o is used as a reverse proxy, an attacker can abuse this vulnerability to send internal state of h2o to backend servers controlled by the attacker or third party. Also, if there is an HTTP endpoint that reflects the traffic sent from the client, an attacker can use that reflector to obtain internal state of h2o.

This internal state includes traffic of other connections in unencrypted form and TLS session tickets.

This vulnerability exists in h2o server with HTTP/3 support, between commit 93af138 and d1f0f65. None of the released versions of h2o are affected by this vulnerability.


CVE Name CVE-2021-43848