jam: Improper Control of Generation of Code
CVE-2025-3841 is a critical-severity improper control of generation of code vulnerability in jam from Wix-incubator, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected jam versions: e87a6fd85cf8fb5ff37b62b2d68f917219d07ae9. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.46% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of jam you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Wix-incubator | jam | e87a6fd85cf8fb5ff37b62b2d68f917219d07ae9 | Not stated |
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
- UnchangedImpact stays within the vulnerable component.
- 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:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 4.8 | Medium | CNA (vuldb.com) |
| CVSS 3.1 | 3.3 | Low | CNA (vuldb.com) |
| CVSS 3.1 | 9.8 | Critical | NVD |
| CVSS 2.0 | 1.7 | Low | CNA (vuldb.com) |
Official description
A vulnerability, which was classified as problematic, was found in wix-incubator jam up to e87a6fd85cf8fb5ff37b62b2d68f917219d07ae9. This affects an unknown part of the file jam.py of the component Jinja2 Template Handler. The manipulation of the argument config['template'] leads to improper neutralization of special elements used in a template engine. It is possible to launch the attack on the local host. The exploit has been disclosed to the public and may be used. This product takes the approach of rolling releases to provide continious delivery. Therefore, version details for affected and updated releases are not available.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Control of Generation of Code
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
How developers prevent this class of flaw
- Refactor your program so that you do not have to dynamically generate code.
- Run your code in a jail or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which code can be executed by your product. Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of your application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.
- Use dynamic tools and techniques that interact with the product using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The product's operation may slow down, but it should not become unstable, crash, or generate incorrect results.
More Improper Control of Generation of Code vulnerabilities (CWE-94)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- github.com/wix-incubator/jam/issues/1Exploit, Issue Tracking
Third-party and government advisories
- vuldb.com/?id.305769Third Party Advisory, VDB Entry
- vuldb.com/?submit.555905Third Party Advisory, VDB Entry
Other references
- vuldb.com/?ctiid.305769Permissions Required, VDB Entry
Recent Improper Control of Generation of Code vulnerabilities
- 9.8 Critical severity
- 7.2 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 7.3 High severity
- 9.9 Critical severity
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