CVE-2026-3099 | Libsoup: libsoup: authentication bypass via digest authentication replay attack

Exp

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: 2026-03-12 Last update: 2026-03-23 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-3099 is rated High Exploit Risk (62/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.54%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

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

Public exploit references (Exploit-DB) for CVE-2026-3099

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-3099

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 2026-04-23 0.37% 0.54% +0.17%
2 2026-03-24 0.15% 0.37% +0.21%
3 2026-03-21 — 0.15% —

Full EPSS history (4 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-3099

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.8 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/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:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
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:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 1.6 3.7 [email protected]
7.3 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/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:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 3.9 3.4 [email protected]

Weakness enumeration for CVE-2026-3099

OS Trackers for CVE-2026-3099

vendor priority summary link
debian not yet assigned CVE-2026-3099 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-2026-3099
redhat medium — https://access.redhat.com/security/cve/CVE-2026-3099
suse medium — https://www.suse.com/security/cve/CVE-2026-3099/
ubuntu low CVE-2026-3099 low priority: Ubuntu including 2 source packages (libsoup2.4, libsoup3), 11 status rows across 7 suites (bionic, focal, jammy, noble, questing, upstream, xenial): deferred 9, needs-triage 2. https://ubuntu.com/security/CVE-2026-3099

Affected software / configurations for CVE-2026-3099

Vendor Product Version Raw CPE
gnome libsoup — cpe:2.3:a:gnome:libsoup:-:*:*:*:*:*:*:*
redhat enterprise_linux 6.0 cpe:2.3:o:redhat:enterprise_linux:6.0:*:*:*:*:*:*:*
redhat enterprise_linux 7.0 cpe:2.3:o:redhat:enterprise_linux:7.0:*:*:*:*:*:*:*
redhat enterprise_linux 8.0 cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
redhat enterprise_linux 9.0 cpe:2.3:o:redhat:enterprise_linux:9.0:*:*:*:*:*:*:*
redhat enterprise_linux 10.0 cpe:2.3:o:redhat:enterprise_linux:10.0:*:*:*:*:*:*:*

References for CVE-2026-3099

URL Tags
https://access.redhat.com/security/cve/CVE-2026-3099 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2442232 Issue Tracking Third Party Advisory
https://gitlab.gnome.org/GNOME/libsoup/-/issues/495 Exploit Issue Tracking Third Party Advisory
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