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GHSA-6jwc-qr2q-7xwj

MediumCVSS 5.8 / 10
Published Aug 3, 2023·Last modified Feb 16, 2024
Affected Components(0)

No affected components available

Description

Impact

RFC 9112 Section 7.1 defined the format of chunk size, chunk data and chunk extension (detailed ABNF is in Appendix section).

In summary:

  • The value of Content-Length header should be a string of 0-9 digits.
  • The chunk size should be a string of hex digits and should split from chunk data using CRLF.
  • The chunk extension shouldn't contain any invisible character.

However, we found that Falcon has following behaviors while disobey the corresponding RFCs.

  • Falcon accepts Content-Length header values that have "+" prefix.
  • Falcon accepts Content-Length header values that written in hexadecimal with "0x" prefix.
  • Falcon accepts "0x" and "+" prefixed chunk size.
  • Falcon accepts LF in chunk extension.

This behavior can lead to desync when forwarding through multiple HTTP parsers, potentially results in HTTP request smuggling and firewall bypassing. Note that while these issues were reproduced in Falcon (the server), the issue is with protocol-http1 which implements the HTTP/1 protocol parser. We have not yet been advised of any real world exploit or practical attack.

Patches

Fixed in protocol-http1 v0.15.1+.

Workarounds

None.

References

https://github.com/socketry/protocol-http1/pull/20

Risk Scores
Base Score
5.8

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the integrity of the data.

Threat Intelligence
5.3

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.64%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Medium severity
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