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Fencer Intel
medium 5.3

CVE-2026-1801 json

Libsoup: libsoup: http request smuggling via malformed chunk headers

published 9mo ago modified 3d ago also EUVD-2026-5176

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 36%
public exploits
0
none known

Summary

A flaw was found in libsoup, an HTTP client/server library. This HTTP Request Smuggling vulnerability arises from non-RFC-compliant parsing in the soup_filter_input_stream_read_line() logic, where libsoup accepts malformed chunk headers, such as lone line feed (LF) characters instead of the required carriage return and line feed (CRLF). A remote attacker can exploit this without authentication or user interaction by sending specially crafted chunked requests. This allows libsoup to parse and process multiple HTTP requests from a single network message, potentially leading to information disclosure.

Patch / fix

  • libsoup3 Ubuntu 24.04 LTS 3.4.4-5ubuntu0.8
  • libsoup2.4 Ubuntu 22.04 LTS 2.74.2-3ubuntu0.8
  • libsoup2.4 Ubuntu 24.04 LTS 2.74.3-6ubuntu1.8
  • libsoup3 Ubuntu Pro 22.04 LTS 3.0.7-0ubuntu1+esm8
  • libsoup2.4 Ubuntu Pro 16.04 LTS 2.52.2-1ubuntu0.3+esm7
  • libsoup2.4 Ubuntu Pro 18.04 LTS 2.62.1-1ubuntu0.4+esm8
  • libsoup2.4 Ubuntu Pro 20.04 LTS 2.70.0-1ubuntu0.5+esm3
  • libsoup2.4 Ubuntu Pro 26.04 LTS 2.74.3-10.1ubuntu5+esm2

ubuntu advisories UBUNTU-CVE-2026-1801

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libsoup2 SLE Micro 5.5, SLE Micro 5.4, SLE Micro 5.3 2.74.2-150400.3.37.1
  • libsoup2 SLE Module for Basesystem 15 SP7 2.74.3-150600.4.36.1
  • libsoup SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Basesystem 15 SP7 3.4.4-150600.3.47.1
  • libsoup Linux Micro 6.0 3.4.2-16.1
  • libsoup Linux Micro 6.1 3.4.4-slfo.1.1_10.1
  • libsoup SLES LTSS Extended Security 12 SP5 2.62.2-5.43.1

suse advisories SUSE-SU-2026:2702-1SUSE-SU-2026:2670-1SUSE-SU-2026:2654-1SUSE-SU-2026:2314-1SUSE-SU-2026:22061-1SUSE-SU-2026:22071-1

  • libsoup2 openSUSE Tumbleweed 2.74.3-21.1

opensuse advisories openSUSE-SU-2026:10917-1

  • libsoup Azure Linux 3.0 3.4.4-12

azure linux advisories AZL-76700

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-1801 updated cvss 5.3

libsoup: libsoup: HTTP Request Smuggling via malformed chunk headers

  • Red Hat Enterprise Linux 6 libsoup Red Hat Enterprise Linux 7 libsoup Red Hat Enterprise Linux 8 libsoup Red Hat Enterprise Linux 9 libsoup Red Hat Enterprise Linux 10 libsoup3
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
9mo ago

Exploit prediction

0.42% chance of exploitation in the next 30 days, higher than 36% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected products

  • 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

Classification

Weakness
  • CWE-444 Inconsistent Interpretation of HTTP Requests

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.