CVE-2023-48230: Cap'n Proto WebSocket message can cause crash
First published: Tue Nov 21 2023(Updated: )
Cap'n Proto is a data interchange format and capability-based RPC system. In versions 1.0 and 1.0.1, when using the KJ HTTP library with WebSocket compression enabled, a buffer underrun can be caused by a remote peer. The underrun always writes a constant value that is not attacker-controlled, likely resulting in a crash, enabling a remote denial-of-service attack. Most Cap'n Proto and KJ users are unlikely to have this functionality enabled and so unlikely to be affected. Maintainers suspect only the Cloudflare Workers Runtime is affected. If KJ HTTP is used with WebSocket compression enabled, a malicious peer may be able to cause a buffer underrun on a heap-allocated buffer. KJ HTTP is an optional library bundled with Cap'n Proto, but is not directly used by Cap'n Proto. WebSocket compression is disabled by default. It must be enabled via a setting passed to the KJ HTTP library via `HttpClientSettings` or `HttpServerSettings`. The bytes written out-of-bounds are always a specific constant 4-byte string `{ 0x00, 0x00, 0xFF, 0xFF }`. Because this string is not controlled by the attacker, maintainers believe it is unlikely that remote code execution is possible. However, it cannot be ruled out. This functionality first appeared in Cap'n Proto 1.0. Previous versions are not affected. This issue is fixed in Cap'n Proto 1.0.1.1.
Credit: security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Capnproto Capnproto | =1.0.0 | |
| Capnproto Capnproto | =1.0.1 |
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Reference Links
Frequently Asked Questions
What is CVE-2023-48230?
CVE-2023-48230 is a vulnerability in the Cap'n Proto library that can cause a crash when receiving a certain WebSocket message.
What is the severity of CVE-2023-48230?
CVE-2023-48230 has a severity rating of 9.8, which is considered critical.
Which software versions are affected by CVE-2023-48230?
Versions 1.0.0 and 1.0.1 of the Cap'n Proto library are affected by CVE-2023-48230.
How can CVE-2023-48230 be exploited?
CVE-2023-48230 can be exploited by sending a specific WebSocket message that triggers a buffer underrun in the Cap'n Proto library.
Is there a fix available for CVE-2023-48230?
Yes, a fix has been released for CVE-2023-48230. It is recommended to update to a version of the Cap'n Proto library that includes the fix.
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