CVE-2021-43848: Unititialized memory access in h2o
First published: Tue Feb 01 2022(Updated: )
h2o is an open source http server. In code prior to the `8c0eca3` commit h2o may attempt to access uninitialized memory. 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. There are no known workarounds. Users of unreleased versions of h2o using HTTP/3 are advised to upgrade immediately.
Credit: security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Dena H2o | <2021-12-20 |
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Reference Links
Frequently Asked Questions
What is CVE-2021-43848?
CVE-2021-43848 is a vulnerability in the h2o HTTP server that allows uninitialized memory to be treated as HTTP/3 frames.
How does CVE-2021-43848 affect h2o?
CVE-2021-43848 affects h2o prior to the `8c0eca3` commit, where it may attempt to access uninitialized memory.
What is the severity of CVE-2021-43848?
The severity of CVE-2021-43848 is high, with a CVSS score of 5.9.
How can I fix CVE-2021-43848?
To fix CVE-2021-43848, update h2o to a version later than the `8c0eca3` commit.
Is there any further information about CVE-2021-43848?
Yes, you can find more information about CVE-2021-43848 in the GitHub commits and security advisories for h2o.
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