CVE-2026-25526
Published: 04 February 2026
Summary
CVE-2026-25526 is a critical-severity Improper Neutralization of Special Elements Used in a Template Engine (CWE-1336) vulnerability in Hubspot Jinjava. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 45.3% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 RA-5 (Vulnerability Monitoring and Scanning) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-25526 is a critical vulnerability in JinJava, a Java-based template engine that adapts Django template syntax for rendering Jinja templates. Prior to versions 2.7.6 and 2.8.3, the ForTag implementation allows attackers to bypass built-in sandbox restrictions, enabling arbitrary Java class instantiation and file access. This flaw, classified under CWE-1336 (Improvable Restriction of Excessive Authentication Attempts, though contextually related to sandbox escape), carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating severe impact potential.
The vulnerability can be exploited remotely by unauthenticated attackers with no user interaction required, due to its network-accessible and low-complexity nature. Successful exploitation grants arbitrary Java code execution within the application's context, allowing attackers to instantiate any Java class and perform unrestricted file operations, effectively defeating JinJava's sandbox protections. This could lead to full system compromise, data exfiltration, or persistence on affected servers processing untrusted templates.
Mitigation is available through upgrading to JinJava versions 2.7.6 or 2.8.3, where the issue has been patched via specific commits (3d02e504d8bbb13bf3fe019e9ca7b51dfce7a998 and c7328dce6030ac718f88974196035edafef24441). The HubSpot security advisory (GHSA-gjx9-j8f8-7j74) and release notes detail these fixes, recommending immediate updates for all deployments using vulnerable versions.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-5336
Vulnerability details
JinJava is a Java-based template engine based on django template syntax, adapted to render jinja templates. Prior to versions 2.7.6 and 2.8.3, JinJava is vulnerable to arbitrary Java execution via bypass through ForTag. This allows arbitrary Java class instantiation and…
more
file access bypassing built-in sandbox restrictions. This issue has been patched in versions 2.7.6 and 2.8.3.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Remote unauthenticated RCE via public-facing JinJava template engine sandbox escape (T1190) directly enables arbitrary Java code execution (T1059) and unrestricted local file access/operations (T1005).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires timely identification, reporting, and correction of flaws like this JinJava sandbox escape vulnerability through vendor patches to versions 2.7.6 or 2.8.3.
Mandates vulnerability scanning to identify the presence of this CVE in deployed JinJava instances, enabling proactive remediation.
Enables monitoring for indicators of exploitation such as anomalous file access or unauthorized Java class instantiations resulting from sandbox bypass.