Use-After-Free Vulnerability in CivetWeb Affecting HTTP/2 Support
CVE-2026-124040

9.2CRITICAL

Key Information:

Vendor

Civetweb

Status
Civetweb
Vendor
CVE Published:
6 November 2026

What is CVE-2026-124040?

CivetWeb versions up to 1.16, when configured with HTTP/2 support, are susceptible to a use-after-free vulnerability in the handle_http2() function. This security issue arises from the improper handling of freed pointers associated with the :method and :path pseudo-headers. Unauthenticated remote attackers can exploit this vulnerability by sending a crafted HEADERS frame that omits these pseudo-headers, potentially abusing server access rules or leading to a server crash. It's crucial for users to review the security configurations and apply necessary updates to mitigate this risk.

Affected Version(s)

civetweb 0 <= 1.16

References

https://github.com/civetweb/civetweb/issues/1379
issue-tracking
https://github.com/civetweb/civetweb
product
https://github.com/civetweb/civetweb/blob/v1.16/src/http2...
technical-description

CVSS V4

Score:
9.2
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
High
Attack Required:
Physical
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

PuH4ck3rX
Lee Keon-Hyeong
.