Vulnerability in GNOME Libsoup
CVE-2026-3099
A flaw was found in Libsoup. The server-side digest authentication implementation in the SoupAuthDomainDigest class does not properly track issued nonces or enforce the required incrementing nonce-count (nc) attribute. This vulnerability allows a remote attacker to capture a single valid authentication header and replay it repeatedly. Consequently, the attacker can bypass authentication and gain unauthorized access to protected resources, impersonating the legitimate user.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:L.
EPSS exploit prediction
EPSS: 0.005 (41.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 42nd percentile — 41.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.001
Affected products
Weakness classification (CWE)
References
- access.redhat.com/security/cve/CVE-2026-3099 (Third Party Advisory, vdb-entry)
- bugzilla.redhat.com/show_bug.cgi (issue-tracking, Third Party Advisory, Issue Tracking)
- gitlab.gnome.org/GNOME/libsoup/-/issues/495 (Exploit, Third Party Advisory, Issue Tracking)
Frequently asked questions
- What is CVE-2026-3099?
- CVE-2026-3099 is a medium-severity vulnerability in GNOME Libsoup, classified under Reusing a Nonce, Key Pair in Encryption. CVSS score: 5.8/10. Published 2026-03-12.
- How severe is CVE-2026-3099?
- Medium severity. CVSS v3 base score is 5.8 out of 10.