CVE-2025-4035 | Libsoup: cookie domain validation bypass via uppercase characters in libsoup

A flaw was found in libsoup. When handling cookies, libsoup clients mistakenly allow cookies to be set for public suffix domains if the domain contains at least two components and includes an uppercase character. This bypasses public suffix protections and could allow a malicious website to set cookies for domains it does not own, potentially leading to integrity issues such as session fixation.

Published: 2025-04-29 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Deferred，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-4035 is rated Low Risk (33.6/100): 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-2025-4035

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 2026-06-07 1.30% 0.26% -1.04%
2 2026-06-06 0.19% 1.30% +1.10%
3 2026-02-23 — 0.19% —

Full EPSS history (9 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-4035

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:L/A:N 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:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 1.4 [email protected]

Weakness enumeration for CVE-2025-4035

OS Trackers for CVE-2025-4035

vendor priority summary link
debian not yet assigned CVE-2025-4035 not yet assigned priority: Debian including 2 source packages (libsoup2.4, libsoup3), 7 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 7. https://security-tracker.debian.org/tracker/CVE-2025-4035
redhat medium — https://access.redhat.com/security/cve/CVE-2025-4035
suse medium — https://www.suse.com/security/cve/CVE-2025-4035/
ubuntu medium CVE-2025-4035 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): deferred 9, ignored 4, needed 2, DNE 1. https://ubuntu.com/security/CVE-2025-4035

Affected software / configurations for CVE-2025-4035

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2025-4035

cvelogic Threat Intelligence