# CVE-2026-3633: Libsoup: libsoup: header and http request injection via crlf injection

Status: published. Published: 2026-03-17. Updated: 2026-11-06.

A flaw was found in libsoup. A remote attacker, by controlling the method parameter of the `soup_message_new()` function, could inject arbitrary headers and additional request data. This vulnerability, known as CRLF (Carriage Return Line Feed) injection, occurs because the method value is not properly escaped during request line construction, potentially leading to HTTP request injection.

## Remediation

- workaround: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 10 (libsoup3): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (libsoup): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (libsoup): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (libsoup): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (libsoup): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 3.9 (low); CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:L; source: CNA: redhat

- CISA KEV: No listing in collected sources

- EPSS: 0.24% as of 2026-11-06; percentile 14.82%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-93

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/security/cve/CVE-2026-3633 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2445128 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://gitlab.gnome.org/GNOME/libsoup/-/issues/484 (CNA: redhat)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-3633; retrieved 2026-11-06; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-3633; retrieved 2026-11-06; source updated Not reported

Revision: 66a633c3d7d4d4341241a8f63e25f00d65608c2dad5aa472c096d090e892f619

Canonical: https://y2.dev/cve/CVE-2026-3633

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