hfs2: Improper Neutralization of Special Elements Used in a Template Engine
CVE-2026-97359 is a critical-severity improper neutralization of special elements used in a template engine vulnerability in hfs2 from Rejetto, with a CVSS 3.1 base score of 10.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected hfs2 versions: 2.0.0 through 2.4.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 5.52% chance of exploitation within 30 days, which is in the top 7.07% of all scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of hfs2 you run against the affected versions below, and install the vendor's latest release.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 10.0 | Critical | CNA (vulncheck.com) |
| CVSS 3.1 | 10.0 | Critical | CNA (vulncheck.com) |
Official description
HFS2 version 2.4.0 and earlier contains a template injection vulnerability in the multipart upload handler that allows unauthenticated attackers to achieve remote code execution by embedding malicious template syntax in a filename. Attackers can craft a filename containing a closing template quoting sequence followed by an exec macro, which bypasses the authorization check in the dispatcher to execute arbitrary commands on the underlying host system.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Special Elements Used in a Template Engine
The product uses a template engine to insert or process externally-influenced input, but it does not neutralize or incorrectly neutralizes special elements or syntax that can be interpreted as template expressions or other code directives when processed by the engine.
How developers prevent this class of flaw
- Choose a template engine that offers a sandbox or restricted mode, or at least limits the power of any available expressions, function calls, or commands.
- Use the template engine's sandbox or restricted mode, if available.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in hfs2
- 7.5 High severity
- 10.0 Critical severity
Recent Improper Neutralization of Special Elements Used in a Template Engine vulnerabilities
- 7.6 High severity
- 8.0 High severity
- 8.8 High severity
- 8.8 High severity
- 9.9 Critical severity
- 10.0 Critical severity
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