CVE-2026-33897
Linuxcontainers Incus ≤ 6.23.0
Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:HSummary
CVE-2026-33897 is a critical-severity Improper Neutralization of Special Elements Used in a Template Engine (CWE-1336) vulnerability in Linuxcontainers Incus. Its CVSS base score is 9.9 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Template Injection (T1221); ranked at the 39th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-33897 is a high-severity vulnerability (CVSS 9.9) affecting Incus, an open-source system container and virtual machine manager, in versions prior to 6.23.0. The issue stems from the implementation of pongo2 templating engine used within Incus instances during various lifecycle stages to process template files. While pongo2 was intended to support file read/write operations confined to the instance's filesystem via a chroot isolation mechanism—allowing templates to read and regenerate files—this chroot feature is entirely skipped, enabling unrestricted access to the host server's filesystem with root privileges (CWE-1336: Improper Neutralization of Special Elements).
An attacker with low privileges (PR:L) on an Incus instance can exploit this over the network (AV:N) with low complexity (AC:L) and no user interaction (UI:N), achieving scope change (S:C) for high impacts on confidentiality, integrity, and availability (C:H/I:H/A:H). By crafting malicious instance template files leveraging pongo2, the attacker can perform arbitrary reads or writes as root on the host system, potentially leading to full host compromise, data exfiltration, persistence, or disruption.
The official GitHub security advisory (GHSA-83xr-5xxr-mh92) confirms that Incus version 6.23.0 addresses the vulnerability by patching the pongo2 chroot bypass. Security practitioners should upgrade to 6.23.0 or later and review instances for untrusted templates.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-16466
Vulnerability Data
Incus is a system container and virtual machine manager. Prior to version 6.23.0, instance template files can be used to cause arbitrary read or writes as root on the host server. Incus allows for pongo2 templates within instances which can…
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be used at various times in the instance lifecycle to template files inside of the instance. This particular implementation of pongo2 within Incus allowed for file read/write but with the expectation that the pongo2 chroot feature would isolate all such access to the instance's filesystem. This was allowed such that a template could theoretically read a file and then generate a new version of said file. Unfortunately the chroot isolation mechanism is entirely skipped by pongo2 leading to easy access to the entire system's filesystem with root privileges. Version 6.23.0 patches the issue.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.3.2V1.3.7V1.3.10
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and static analysis can discover missing neutralization of template directives.
Input validation rejects or sanitizes untrusted data before it reaches the template engine, stopping injection of special syntax.
Security engineering principles require use of safe templating APIs and proper escaping of external input.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly require proper input neutralization in template engines to prevent injection.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can detect template-injection flaws but does not itself implement neutralization controls.
Secure development life cycle mandates input validation and sanitization that directly prevents template-injection weaknesses.
Application security requirements explicitly call for neutralizing special elements in template engines.
Secure architecture principles reduce the likelihood of unsafe template processing but do not prescribe specific neutralization techniques.
Secure coding standards require proper escaping or sandboxing of template directives, directly mitigating CWE-1336.