CVE-2023-38697

What it is

protocol-http1 provides a low-level implementation of the HTTP/1 protocol. RFC 9112 Section 7.1 defined the format of chunk size, chunk data and chunk extension. 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, and the chunk extension shouldn't contain any invisible character. However, Falcon has following behaviors while disobey the corresponding RFCs: accepting Content-Length header values that have `+` prefix, accepting Content-Length header values that written in hexadecimal with `0x` prefix, accepting `0x` and `+` prefixed chunk size, and accepting 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. This issue is fixed in `protocol-http1` v0.15.1. There are no known workarounds.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

0.8% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2023-08-04 18:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 06:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.8% in the next 30 days (EPSS).
• Severity: 5.8 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2023-08-04 18:15 UTC

Last modified

2026-06-17 06:10 UTC

Exploit probability

0.8% · EPSS, next 30 days

Weakness

CWE-444

Record status

Modified

Affected

• Socketry protocol-http1 < 0.15.1

Attack profile CVSS 3.1 · 5.8

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

None

Integrity

Low

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2023-38697.md and follow it. Check whether this project is affected by CVE-2023-38697. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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