CVE-2025-4476
Libsoup: null pointer dereference in libsoup may lead to denial of service
- Published
- May 16, 2025
- Updated
- Jun 30, 2026
- Assigning CNA
- redhat
- Evidence observed
- Aug 25, 2026
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:LLow · next 30 days
- Percentile
- 32.3%
- Model date
- Sep 21, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
Summary
A denial-of-service vulnerability has been identified in the libsoup HTTP client library. This flaw can be triggered when a libsoup client receives a 401 (Unauthorized) HTTP response containing a specifically crafted domain parameter within the WWW-Authenticate header. Processing this malformed header can lead to a crash of the client application using libsoup. An attacker could exploit this by setting up a malicious HTTP server. If a user's application using the vulnerable libsoup library connects to this malicious server, it could result in a denial-of-service. Successful exploitation requires tricking a user's client application into connecting to the attacker's malicious server.
Sources
1Python test client that sends HTTP GET requests with oversized Authorization headers to trigger header-parsing bugs like CVE-2025-4476. For authorized lab testing and research only.
Responsible use
Use vulnerability information only on systems you own or are authorized to test. Kitploit links to public research metadata and does not store exploit code or malicious payloads.