boazsegev facil.io up to 0.7.6 HTTP1.1 Chunked Transfer Encoding Parser http1_parser.h denial of service

Summaryinfo

A vulnerability classified as critical has been found in boazsegev facil.io up to 0.7.6. Affected by this vulnerability is an unknown functionality of the file http1_parser.h of the component HTTP1.1 Chunked Transfer Encoding Parser. This manipulation causes denial of service. This vulnerability is registered as CVE-2026-66731. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in boazsegev facil.io up to 0.7.6. It has been declared as critical. Affected by this vulnerability is some unknown processing of the file http1_parser.h of the component HTTP1.1 Chunked Transfer Encoding Parser. The manipulation with an unknown input leads to a denial of service vulnerability. The CWE definition for the vulnerability is CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. As an impact it is known to affect availability. The summary by CVE is:

facil.io 0.7.5 through 0.7.6 contains a denial-of-service vulnerability in the HTTP/1.1 chunked transfer encoding parser that allows unauthenticated remote attackers to crash the server by sending a negative chunk size value. Attackers can send a single POST request with a Transfer-Encoding: chunked header containing a leading minus sign in the chunk size field, causing the parser in http1_parser.h to compute a large positive integer from the negated value, corrupting internal state and moving the read pointer into unmapped memory resulting in a fault.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-66731 since 07/27/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• boazsegev

Name

• facil.io

Version

• 0.7.0
• 0.7.1
• 0.7.2
• 0.7.3
• 0.7.4
• 0.7.5
• 0.7.6

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

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