CVE-2026-9558

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Summary

CVECVE-2026-9558
StatePUBLISHED
AssignerMautic
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-29 11:16:17 UTC
Updated2026-05-29 15:39:34 UTC
DescriptionA Server-Side Template Injection (SSTI) vulnerability exists in Mautic's theme engine. The platform renders uploaded Twig templates without a sandbox or strict function restrictions. Authenticated users with permissions to create or upload themes can abuse this to execute arbitrary code on the hosting server (Remote Code Execution) or access restricted system files and configuration settings.

Risk And Classification

Primary CVSS: v3.1 9.9 CRITICAL from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Problem Types: CWE-1336 | CWE-1336 CWE-1336 Improper Neutralization of Special Elements Used in a Template Engine

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.9CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
3.1CNACVSS9.9CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

References

ReferenceSourceLinkTags
github.com/mautic/mautic/security/advisories/GHSA-9fx4-7cmj-47vg [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Onurcan Genç (@onurcangnc) (en)

CNA: Daniel Zhang (@xfer0) (en)

CNA: Tuan Do (@Entropt) (en)

CNA: Patryk Gruszka (@patrykgruszka) (en)

CNA: John Linhart (@escopecz) (en)

CNA: Leuchtfeuer Digital Marketing (@Leuchtfeuer) (en)

Additional Advisory Data

Workarounds

CNA: There are no official workarounds. To mitigate this vulnerability without upgrading, restrict theme upload and creation permissions (core:themes:create) to only highly trusted administrators.

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