tinypool: Improperly Controlled Modification of Object Prototype Attributes
CVE-2026-104848 is a critical-severity improperly controlled modification of object prototype attributes vulnerability in tinypool from Tinylibs, with a CVSS 4.0 base score of 9.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected tinypool versions: < 2.1.1. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.5% 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 tinypool 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
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.
- Attack requirements
- PresentThe target must be in a specific state or configuration for the attack to work.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Confidentiality (vulnerable system)
- HighSerious loss of confidentiality on the vulnerable system.
- Integrity (vulnerable system)
- HighSerious loss of integrity on the vulnerable system.
- Availability (vulnerable system)
- HighSerious loss of availability on the vulnerable system.
- Confidentiality (other systems)
- HighSerious loss of confidentiality on systems beyond the vulnerable one.
- Integrity (other systems)
- HighSerious loss of integrity on systems beyond the vulnerable one.
- Availability (other systems)
- HighSerious loss of availability on systems beyond the vulnerable one.
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. Scored by CNA (github.com).
Official description
Tinypool is a minimal Node.js worker thread pool implementation. Prior to 2.1.1, Tinypool constructs ThreadPool.options from a normal options object and reads the execArgv and env worker options in dist/index.js, allowing values inherited from a polluted Object.prototype to be copied into own properties and passed to worker_threads.Worker. An attacker who can first pollute either property can cause each newly spawned worker to load attacker-selected JavaScript through command-line preload arguments or NODE_OPTIONS, resulting in code execution with the host process's privileges and possible access to CI secrets, signing material, or build artifacts. This issue is fixed in version 2.1.1.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improperly Controlled Modification of Object Prototype Attributes
The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.
How developers prevent this class of flaw
- By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.
- By blocking modifications of attributes that resolve to object prototype, such as proto or prototype, this weakness can be mitigated.
- When handling untrusted objects, validating using a schema can be used.
More Improperly Controlled Modification of Object Prototype Attributes vulnerabilities (CWE-1321)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
References
Patches and release notes
Other vulnerabilities in tinypool
- 9.5 Critical severity
Recent Improperly Controlled Modification of Object Prototype Attributes vulnerabilities
- 9.2 Critical severity
- 8.3 High severity
- 8.4 High severity
- 7.6 High severity
- 8.3 High severity
- 9.1 Critical severity
Spotted an error? Tell us.