# CVE-2026-103399: Libsoup: soupserver: http/1 request smuggling via undrained expect: 100-continue body

CVE-2026-103399 is fixed in 22 products on 1 platform, first by gir1.2-soup-2.4 2.62.1-1ubuntu0.4+esm10, released September 30, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-103399
- Priority: Routine
- CVSS: 5.3 (Moderate)
- EPSS: 0.0025
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 30, 2026
- Weakness: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-103399

## Description

A flaw was found in SoupServer (libsoup). When an HTTP/1.x client sends a request with Expect: 100-continue and a request body, and SoupServer returns an early final (non-1xx) response before the body is read, the server neither drains the declared body bytes nor closes the connection. On a keep-alive connection, those leftover bytes are interpreted as a subsequent HTTP request. A remote, unauthenticated attacker can place a complete HTTP request in the body and cause SoupServer to process that smuggled request, leading to unintended request handling.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | gir1.2-soup-2.4 Ubuntu 18.04.6 LTS (bionic) | 2.62.1-1ubuntu0.4+esm10 | [gir1.2-soup-2.4 2.62.1-1ubuntu0.4+esm10](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-gir1.2-soup-2.4-2.62.1-1ubuntu0.4-esm10.md) | Sep 30, 2026 |
| Linux | gir1.2-soup-2.4 Ubuntu 20.04 LTS (focal) | 2.70.0-1ubuntu0.5+esm5 | [gir1.2-soup-2.4 2.70.0-1ubuntu0.5+esm5](https://patchblox.com/security/data/fix/linux/ubuntu-focal-gir1.2-soup-2.4-2.70.0-1ubuntu0.5-esm5.md) | Sep 30, 2026 |
| Linux | gir1.2-soup-2.4 Ubuntu 22.04.1 LTS (jammy) | 2.74.2-3ubuntu0.10 | [gir1.2-soup-2.4 2.74.2-3ubuntu0.10](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-gir1.2-soup-2.4-2.74.2-3ubuntu0.10.md) | Sep 30, 2026 |
| Linux | gir1.2-soup-2.4 Ubuntu 24.04.5 LTS (noble) | 2.74.3-6ubuntu1.10 | [gir1.2-soup-2.4 2.74.3-6ubuntu1.10](https://patchblox.com/security/data/fix/linux/ubuntu-noble-gir1.2-soup-2.4-2.74.3-6ubuntu1.10.md) | Sep 30, 2026 |
| Linux | gir1.2-soup-2.4 Ubuntu 26.04.1 LTS (resolute) | 2.74.3-10.1ubuntu5+esm4 | [gir1.2-soup-2.4 2.74.3-10.1ubuntu5+esm4](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-gir1.2-soup-2.4-2.74.3-10.1ubuntu5-esm4.md) | Sep 30, 2026 |
| Linux | gir1.2-soup-3.0 Ubuntu 22.04.1 LTS (jammy) | 3.0.7-0ubuntu1+esm10 | [gir1.2-soup-3.0 3.0.7-0ubuntu1+esm10](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-gir1.2-soup-3.0-3.0.7-0ubuntu1-esm10.md) | Sep 30, 2026 |
| Linux | gir1.2-soup-3.0 Ubuntu 24.04.5 LTS (noble) | 3.4.4-5ubuntu0.10 | [gir1.2-soup-3.0 3.4.4-5ubuntu0.10](https://patchblox.com/security/data/fix/linux/ubuntu-noble-gir1.2-soup-3.0-3.4.4-5ubuntu0.10.md) | Sep 30, 2026 |
| Linux | gir1.2-soup-3.0 Ubuntu 26.04.1 LTS (resolute) | 3.6.6-1ubuntu0.2 | [gir1.2-soup-3.0 3.6.6-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-gir1.2-soup-3.0-3.6.6-1ubuntu0.2.md) | Sep 30, 2026 |
| Linux | libsoup amzn 2023 | 2.72.0-6.amzn2023.0.16 | [ALAS2023-2026-3212](https://patchblox.com/security/data/fix/linux/alas2023-2026-3212.md) | Nov 7, 2026 |
| Linux | libsoup opensuse-leap 16.0 | 3.6.6-160000.5.1 | [OPENSUSE-SU-2026:22181-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-22181-1.md) | Nov 7, 2026 |
| Linux | libsoup sles 15.6 | 3.4.4-150600.3.62.1 | [SUSE-SU-2026:5062-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5062-1.md) | Nov 7, 2026 |
| Linux | libsoup sles 15.7 | 3.4.4-150600.3.62.1 | [SUSE-SU-2026:5062-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5062-1.md) | Nov 7, 2026 |
| Linux | libsoup sles 16.0 | 3.6.6-160000.5.1 | [SUSE-SU-2026:24470-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-24470-1.md) | Nov 7, 2026 |
| Linux | libsoup-2.4-1 Ubuntu 24.04.5 LTS (noble) | 2.74.3-6ubuntu1.10 | [libsoup-2.4-1 2.74.3-6ubuntu1.10](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libsoup-2.4-1-2.74.3-6ubuntu1.10.md) | Sep 30, 2026 |
| Linux | libsoup-2.4-1 Ubuntu 26.04.1 LTS (resolute) | 2.74.3-10.1ubuntu5+esm4 | [libsoup-2.4-1 2.74.3-10.1ubuntu5+esm4](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libsoup-2.4-1-2.74.3-10.1ubuntu5-esm4.md) | Sep 30, 2026 |
| Linux | libsoup-3.0-0 Ubuntu 22.04.1 LTS (jammy) | 3.0.7-0ubuntu1+esm10 | [libsoup-3.0-0 3.0.7-0ubuntu1+esm10](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libsoup-3.0-0-3.0.7-0ubuntu1-esm10.md) | Sep 30, 2026 |
| Linux | libsoup-3.0-0 Ubuntu 24.04.5 LTS (noble) | 3.4.4-5ubuntu0.10 | [libsoup-3.0-0 3.4.4-5ubuntu0.10](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libsoup-3.0-0-3.4.4-5ubuntu0.10.md) | Sep 30, 2026 |
| Linux | libsoup-3.0-0 Ubuntu 26.04.1 LTS (resolute) | 3.6.6-1ubuntu0.2 | [libsoup-3.0-0 3.6.6-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libsoup-3.0-0-3.6.6-1ubuntu0.2.md) | Sep 30, 2026 |
| Linux | libsoup-3.0-common Ubuntu 22.04.1 LTS (jammy) | 3.0.7-0ubuntu1+esm10 | [libsoup-3.0-common 3.0.7-0ubuntu1+esm10](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libsoup-3.0-common-3.0.7-0ubuntu1-esm10.md) | Sep 30, 2026 |
| Linux | libsoup-3.0-common Ubuntu 24.04.5 LTS (noble) | 3.4.4-5ubuntu0.10 | [libsoup-3.0-common 3.4.4-5ubuntu0.10](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libsoup-3.0-common-3.4.4-5ubuntu0.10.md) | Sep 30, 2026 |
| Linux | libsoup-3.0-common Ubuntu 26.04.1 LTS (resolute) | 3.6.6-1ubuntu0.2 | [libsoup-3.0-common 3.6.6-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libsoup-3.0-common-3.6.6-1ubuntu0.2.md) | Sep 30, 2026 |
| Linux | libsoup-3.0-tests Ubuntu 22.04.1 LTS (jammy) | 3.0.7-0ubuntu1+esm10 | [libsoup-3.0-tests 3.0.7-0ubuntu1+esm10](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libsoup-3.0-tests-3.0.7-0ubuntu1-esm10.md) | Sep 30, 2026 |
| Linux | libsoup-3.0-tests Ubuntu 24.04.5 LTS (noble) | 3.4.4-5ubuntu0.10 | [libsoup-3.0-tests 3.4.4-5ubuntu0.10](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libsoup-3.0-tests-3.4.4-5ubuntu0.10.md) | Sep 30, 2026 |
| Linux | libsoup-3.0-tests Ubuntu 26.04.1 LTS (resolute) | 3.6.6-1ubuntu0.2 | [libsoup-3.0-tests 3.6.6-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libsoup-3.0-tests-3.6.6-1ubuntu0.2.md) | Sep 30, 2026 |
| Linux | libsoup-debuginfo amzn 2023 | 2.72.0-6.amzn2023.0.16 | [ALAS2023-2026-3212](https://patchblox.com/security/data/fix/linux/alas2023-2026-3212.md) | Nov 7, 2026 |
| Linux | libsoup-debugsource amzn 2023 | 2.72.0-6.amzn2023.0.16 | [ALAS2023-2026-3212](https://patchblox.com/security/data/fix/linux/alas2023-2026-3212.md) | Nov 7, 2026 |
| Linux | libsoup-devel amzn 2023 | 2.72.0-6.amzn2023.0.16 | [ALAS2023-2026-3212](https://patchblox.com/security/data/fix/linux/alas2023-2026-3212.md) | Nov 7, 2026 |
| Linux | libsoup-doc amzn 2023 | 2.72.0-6.amzn2023.0.16 | [ALAS2023-2026-3212](https://patchblox.com/security/data/fix/linux/alas2023-2026-3212.md) | Nov 7, 2026 |
| Linux | libsoup-gnome-2.4-1 Ubuntu 24.04.5 LTS (noble) | 2.74.3-6ubuntu1.10 | [libsoup-gnome-2.4-1 2.74.3-6ubuntu1.10](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libsoup-gnome-2.4-1-2.74.3-6ubuntu1.10.md) | Sep 30, 2026 |
| Linux | libsoup-gnome-2.4-1 Ubuntu 26.04.1 LTS (resolute) | 2.74.3-10.1ubuntu5+esm4 | [libsoup-gnome-2.4-1 2.74.3-10.1ubuntu5+esm4](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libsoup-gnome-2.4-1-2.74.3-10.1ubuntu5-esm4.md) | Sep 30, 2026 |
| Linux | libsoup-gnome2.4-1 Ubuntu 18.04.6 LTS (bionic) | 2.62.1-1ubuntu0.4+esm10 | [libsoup-gnome2.4-1 2.62.1-1ubuntu0.4+esm10](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libsoup-gnome2.4-1-2.62.1-1ubuntu0.4-esm10.md) | Sep 30, 2026 |
| Linux | libsoup-gnome2.4-1 Ubuntu 20.04 LTS (focal) | 2.70.0-1ubuntu0.5+esm5 | [libsoup-gnome2.4-1 2.70.0-1ubuntu0.5+esm5](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libsoup-gnome2.4-1-2.70.0-1ubuntu0.5-esm5.md) | Sep 30, 2026 |
| Linux | libsoup-gnome2.4-1 Ubuntu 22.04.1 LTS (jammy) | 2.74.2-3ubuntu0.10 | [libsoup-gnome2.4-1 2.74.2-3ubuntu0.10](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libsoup-gnome2.4-1-2.74.2-3ubuntu0.10.md) | Sep 30, 2026 |
| Linux | libsoup2 sles 15.6 | 2.74.3-150600.4.42.1 | [SUSE-SU-2026:4703-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4703-1.md) | Nov 7, 2026 |
| Linux | libsoup2 sles 15.7 | 2.74.3-150600.4.42.1 | [SUSE-SU-2026:4703-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4703-1.md) | Nov 7, 2026 |
| Linux | libsoup2.4-1 Ubuntu 18.04.6 LTS (bionic) | 2.62.1-1ubuntu0.4+esm10 | [libsoup2.4-1 2.62.1-1ubuntu0.4+esm10](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libsoup2.4-1-2.62.1-1ubuntu0.4-esm10.md) | Sep 30, 2026 |
| Linux | libsoup2.4-1 Ubuntu 20.04 LTS (focal) | 2.70.0-1ubuntu0.5+esm5 | [libsoup2.4-1 2.70.0-1ubuntu0.5+esm5](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libsoup2.4-1-2.70.0-1ubuntu0.5-esm5.md) | Sep 30, 2026 |
| Linux | libsoup2.4-1 Ubuntu 22.04.1 LTS (jammy) | 2.74.2-3ubuntu0.10 | [libsoup2.4-1 2.74.2-3ubuntu0.10](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libsoup2.4-1-2.74.2-3ubuntu0.10.md) | Sep 30, 2026 |
| Linux | libsoup2.4-common Ubuntu 22.04.1 LTS (jammy) | 2.74.2-3ubuntu0.10 | [libsoup2.4-common 2.74.2-3ubuntu0.10](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libsoup2.4-common-2.74.2-3ubuntu0.10.md) | Sep 30, 2026 |
| Linux | libsoup2.4-common Ubuntu 24.04.5 LTS (noble) | 2.74.3-6ubuntu1.10 | [libsoup2.4-common 2.74.3-6ubuntu1.10](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libsoup2.4-common-2.74.3-6ubuntu1.10.md) | Sep 30, 2026 |
| Linux | libsoup2.4-common Ubuntu 26.04.1 LTS (resolute) | 2.74.3-10.1ubuntu5+esm4 | [libsoup2.4-common 2.74.3-10.1ubuntu5+esm4](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libsoup2.4-common-2.74.3-10.1ubuntu5-esm4.md) | Sep 30, 2026 |
| Linux | libsoup2.4-tests Ubuntu 20.04 LTS (focal) | 2.70.0-1ubuntu0.5+esm5 | [libsoup2.4-tests 2.70.0-1ubuntu0.5+esm5](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libsoup2.4-tests-2.70.0-1ubuntu0.5-esm5.md) | Sep 30, 2026 |
| Linux | libsoup2.4-tests Ubuntu 22.04.1 LTS (jammy) | 2.74.2-3ubuntu0.10 | [libsoup2.4-tests 2.74.2-3ubuntu0.10](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libsoup2.4-tests-2.74.2-3ubuntu0.10.md) | Sep 30, 2026 |
| Linux | libsoup2.4-tests Ubuntu 24.04.5 LTS (noble) | 2.74.3-6ubuntu1.10 | [libsoup2.4-tests 2.74.3-6ubuntu1.10](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libsoup2.4-tests-2.74.3-6ubuntu1.10.md) | Sep 30, 2026 |
| Linux | libsoup2.4-tests Ubuntu 26.04.1 LTS (resolute) | 2.74.3-10.1ubuntu5+esm4 | [libsoup2.4-tests 2.74.3-10.1ubuntu5+esm4](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libsoup2.4-tests-2.74.3-10.1ubuntu5-esm4.md) | Sep 30, 2026 |
| Linux | libsoup3 amzn 2023 | 3.7.3-1.amzn2023 | [ALAS2023-2026-3240](https://patchblox.com/security/data/fix/linux/alas2023-2026-3240.md) | Nov 7, 2026 |
| Linux | libsoup3-debuginfo amzn 2023 | 3.7.3-1.amzn2023 | [ALAS2023-2026-3240](https://patchblox.com/security/data/fix/linux/alas2023-2026-3240.md) | Nov 7, 2026 |
| Linux | libsoup3-debugsource amzn 2023 | 3.7.3-1.amzn2023 | [ALAS2023-2026-3240](https://patchblox.com/security/data/fix/linux/alas2023-2026-3240.md) | Nov 7, 2026 |
| Linux | libsoup3-devel amzn 2023 | 3.7.3-1.amzn2023 | [ALAS2023-2026-3240](https://patchblox.com/security/data/fix/linux/alas2023-2026-3240.md) | Nov 7, 2026 |
| Linux | libsoup3-doc amzn 2023 | 3.7.3-1.amzn2023 | [ALAS2023-2026-3240](https://patchblox.com/security/data/fix/linux/alas2023-2026-3240.md) | Nov 7, 2026 |

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