CVE-2025-4476 | Libsoup: null pointer dereference in libsoup may lead to denial of service

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.

Published: 2025-05-16 Last update: 2026-05-06 Assigner: [email protected] Source: [email protected]
NVD Status：Deferred，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-4476 is rated Low Risk (34.7/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.26%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-4476

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-03-12 0.06% 0.26% +0.20%
2 2026-01-30 0.03% 0.06% +0.03%
3 2025-11-21 — 0.03% —

Full EPSS history (7 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-4476

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 2.8 1.4 [email protected]

Weakness enumeration for CVE-2025-4476

GitHub Security Advisory for CVE-2025-4476

GHSA-qgq4-89p9-qfrh · Severity: medium — A denial-of-service vulnerability has been identified in the libsoup HTTP client library. This...

OS Trackers for CVE-2025-4476

vendor priority summary link
debian not yet assigned CVE-2025-4476 not yet assigned priority: Debian including 2 source packages (libsoup2.4, libsoup3), 7 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 4, open 3. https://security-tracker.debian.org/tracker/CVE-2025-4476
redhat low — https://access.redhat.com/security/cve/CVE-2025-4476
suse medium CVE-2025-4476 severity moderate: SUSE including 55 source package names (13.2-9.12:curl-8.14.1-slfo.1.1_4.1, 13.2-9.12:libcurl-mini4-8.14.1-slfo.1.1_4.1, …), 196 product×package rows across 48 product lines (Container suse/sl-micro/6.0/baremetal-os-container, Container suse/sl-micro/6.0/base-os-container, … (48 product lines)): Fixed 196. https://www.suse.com/security/cve/CVE-2025-4476/
ubuntu medium CVE-2025-4476 medium priority: Ubuntu including 2 source packages (libsoup2.4, libsoup3), 16 status rows across 9 suites (bionic, focal, jammy, noble, oracular, plucky, questing, upstream, xenial): released 11, needs-triage 2, not-affected 2, DNE 1. https://ubuntu.com/security/CVE-2025-4476

Affected software / configurations for CVE-2025-4476

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2025-4476

cvelogic Threat Intelligence