CVE-2023-34102 is a high-severity (CVSS 8.3) Improper Input Validation vulnerability in avo. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for avo — see the affected versions and patch details below.
Possible unsafe reflection / partial denial of service in avo
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-34102.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
avo💎avoReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The polymorphic field type stores the classes to operate on when updating a record with user input, and does not validate them in the back end. This can lead to unexpected behavior, remote code execution, or application crashes when viewing a manipulated record.
Details
After reviewing the polymorphic field implementation and performing some black box approaches, we identified a potential security issue related to the use of safe_constantize / constantize. This Rails functionality is capable of searching for classes within the Rails context and returning the class for further use. Because Avo does not validate user input when updating or creating a new polymorphic resource, it is possible to create database entries with completely different or invalid class names than the preselected ones. Avo assumes that the class specified by the user request is a valid one and attempts to work with it, which may result in dangerous behavior and code execution.
PoC
In the test scenario we choose the demo app and the review resource which has a polymorphic reviewable field.
Intercepting the request and switching the review[reviewable_type] from “Fish” to “File” which is a real class inside Rails
Corrupting the database with unusable classes will cause a crash at the application while viewing the new record or the index view (partial DoS)
Manual delete the corrupted resource in order to recover the applications functionality
Of course it is possible to use other class names or namespaces. The local development environment displays the backend error message when visiting a corrupted record. Avo is trying to apply a scope to this class that does not exist.
Specifying an invalid class name in the parameter will cause the application to crash again while trying constanize the provided string
Impact
The final exploitation of this vulnerability requires more time than is provided in this assessment, but initial testing of the post request shows the potential critical risk. The classes could be instantiated at any point in the code and this could also lead to code execution.
Recommendation
Avo should be configured to never trust user-supplied input, especially when defining classes for records. In this particular case, Avo can evaluate the options list given for the polymorphic field and only allow strings from that list. With this white-list approach, an attacker cannot supply unintended classes.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | avo | all versions | 2.33.3bundle update avo --conservative |
| 💎RubyGems | avo | ≥ 3.0.0.pre1 | No fix |
Affected Products
avoavohqResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for avo, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update avo to 2.33.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-34102 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
Frequently Asked Questions
Is CVE-2023-34102 in your dependencies?
Find it across RubyGems, including transitive dependencies.