Description
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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| — | libsoup | < 3.6.6 | 3.6.6 |
| Red Hat | Red Hat Enterprise Linux 10 | — | — |
| Red Hat | Red Hat Enterprise Linux 6 | — | — |
| Red Hat | Red Hat Enterprise Linux 7 | — | — |
| Red Hat | Red Hat Enterprise Linux 8 | — | — |
| Red Hat | Red Hat Enterprise Linux 9 | — | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 13 | libsoup2.4 | No fix yet | — |
| Debian 13 | libsoup3 | 3.6.5-2 | — |
| Debian 12 | libsoup3 +1 | No fix yet | — |
| Debian 11 | libsoup2.4 | 2.72.0-2+deb11u3 | DLA-4398-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 24.04 LTS | libsoup2.4 | 2.74.3-6ubuntu1.5 | USN-7543-1 |
| Ubuntu 24.04 LTS | libsoup3 | 3.4.4-5ubuntu0.4 | USN-7543-1 |
| Ubuntu 22.04 LTS | libsoup2.4 | 2.74.2-3ubuntu0.5 | USN-7543-1 |
| Ubuntu 20.04 LTS | libsoup2.4 | 2.70.0-1ubuntu0.5 | USN-7543-1 |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 22.04 LTS | libsoup3 | 3.0.7-0ubuntu1+esm4 | USN-7543-1 |
| Ubuntu Pro 18.04 LTS | libsoup2.4 | 2.62.1-1ubuntu0.4+esm4 | USN-7543-1 |
| Ubuntu Pro 16.04 LTS | libsoup2.4 | 2.52.2-1ubuntu0.3+esm3 | USN-7543-1 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | libsoup | 3.4.4-150600.3.10.1 | SUSE-SU-2025:01812-1 |
| SLES 15 SP7 | libsoup2 | 2.74.3-150600.4.24.1 | SUSE-SU-2026:0574-1 |
| SLES 15 SP6 | libsoup | 3.4.4-150600.3.10.1 | SUSE-SU-2025:01812-1 |
| SLES 15 SP6 | libsoup2 | 2.74.3-150600.4.24.1 | SUSE-SU-2026:0574-1 |
| SLES 15 SP5 | libsoup | 3.0.4-150400.3.10.1 | SUSE-SU-2025:01817-1 |
| SLES 15 SP5 | libsoup2 | 2.74.2-150400.3.26.1 | SUSE-SU-2026:0497-1 |
| SLES 15 SP4 | libsoup | 3.0.4-150400.3.10.1 | SUSE-SU-2025:01817-1 |
| SLES 15 SP4 | libsoup2 | 2.74.2-150400.3.26.1 | SUSE-SU-2026:0497-1 |
| SLES 12 SP5 | libsoup | 2.62.2-5.34.1 | SUSE-SU-2026:0703-1 |
Show 13 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 15 SP6 | libsoup2 | 2.74.3-150600.4.24.1 | SUSE-SU-2026:0574-1 |
| SLES for SAP 15 SP5 | libsoup | 3.0.4-150400.3.10.1 | SUSE-SU-2025:01817-1 |
| SLES for SAP 15 SP5 | libsoup2 | 2.74.2-150400.3.26.1 | SUSE-SU-2026:0497-1 |
| SLES for SAP 15 SP4 | libsoup | 3.0.4-150400.3.10.1 | SUSE-SU-2025:01817-1 |
| SLES for SAP 15 SP4 | libsoup2 | 2.74.2-150400.3.26.1 | SUSE-SU-2026:0497-1 |
| SLE Micro 6.1 | libsoup | 3.4.4-slfo.1.1_4.1 | SUSE-SU-2025:20598-1 |
| SLE Micro 6.0 | libsoup | 3.4.2-8.1 | SUSE-SU-2025:20453-1 |
| SLE Micro 5.5 | libsoup2 | 2.74.2-150400.3.26.1 | SUSE-SU-2026:0497-1 |
| SLE Micro 5.4 | libsoup2 | 2.74.2-150400.3.26.1 | SUSE-SU-2026:0497-1 |
| SLE Micro 5.3 | libsoup2 | 2.74.2-150400.3.26.1 | SUSE-SU-2026:0497-1 |
| SLE Micro 5.2 | libsoup | 2.68.4-150200.4.27.1 | SUSE-SU-2026:0469-1 |
| SLE HPC 15 SP5 | libsoup | 3.0.4-150400.3.10.1 | SUSE-SU-2025:01817-1 |
| SLE HPC 15 SP5 | libsoup2 | 2.74.2-150400.3.26.1 | SUSE-SU-2026:0497-1 |
| SLE HPC 15 SP4 | libsoup | 3.0.4-150400.3.10.1 | SUSE-SU-2025:01817-1 |
| SLE HPC 15 SP4 | libsoup2 | 2.74.2-150400.3.26.1 | SUSE-SU-2026:0497-1 |
| SUSE Manager Server 4.3 | libsoup | 3.0.4-150400.3.10.1 | SUSE-SU-2025:01817-1 |
| SUSE Manager Proxy 4.3 | libsoup | 3.0.4-150400.3.10.1 | SUSE-SU-2025:01817-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | libsoup | 3.6.5-5.1 | openSUSE-SU-2025:15185-1 |
| openSUSE Tumbleweed | libsoup2 | 2.74.3-15.1 | openSUSE-SU-2026:10166-1 |
| openSUSE Leap 16.0 | libsoup2 | 2.74.3-160000.4.1 | openSUSE-SU-2026:20354-1 |
| openSUSE Leap 15.6 | libsoup | 3.4.4-150600.3.10.1 | SUSE-SU-2025:01812-1 |
| openSUSE Leap 15.6 | libsoup2 | 2.74.3-150600.4.24.1 | SUSE-SU-2026:0574-1 |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | libsoup +2 | 2.72.0-6.amzn2023.0.8 | ALAS2023-2025-1310 |
| Amazon Linux 2023 | libsoup3 +2 | 3.6.5-52.amzn2023 | ALAS2023-2025-1233 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | libsoup | 3.4.4-7 | — |
| Azure Linux 2 (CBL-Mariner) | libsoup | 3.0.4-7 | — |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.
GitHub 1 repository
-
soltanali0/CVE-2025-4476-Exploit ★ 0 · Oct 9, 2025
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 15
- USN-7543-1 libsoup3, libsoup2.4 vulnerabilities Ubuntu Security Notices (USN) · Jun 25, 2026
- openSUSE-SU-2026:20354-1 Security update for libsoup2 SUSE / openSUSE Security Updates · Mar 23, 2026
- openSUSE-SU-2026:10166-1 libsoup-2_4-1-2.74.3-15.1 on GA media SUSE / openSUSE Security Updates · Mar 23, 2026
- openSUSE-SU-2025:15185-1 libsoup-3_0-0-3.6.5-5.1 on GA media SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2026:0574-1 Security update for libsoup2 SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2026:0497-1 Security update for libsoup2 SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2026:0469-1 Security update for libsoup SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2026:0703-1 Security update for libsoup SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:20598-1 Security update for libsoup SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:20453-1 Security update for libsoup SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:01812-1 Security update for libsoup SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:01817-1 Security update for libsoup SUSE / openSUSE Security Updates · Feb 4, 2026
- DLA-4398-1 libsoup2.4 - security update Debian Security (DSA / DLA) · Dec 9, 2025
- ALAS2023-2025-1310 Moderate: libsoup security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Dec 8, 2025
- ALAS2023-2025-1233 Moderate: libsoup3 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Oct 27, 2025