CVE-2026-44292 — protobufjs
MEDIUMCVE-2026-44292 is a medium-severity (CVSS 5.3) vulnerability in protobufjs. A fix is available for protobufjs — see the affected versions and patch details below.
protobufjs: Prototype injection in generated message constructors
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44292.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-44292 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
protobufjsnpmDescription
Summary
protobufjs generated message constructors copied enumerable properties from a provided properties object without filtering the __proto__ key. If an application constructed a message from an attacker-controlled plain object, an own enumerable __proto__ property could alter the prototype of that individual message instance.
Impact
An attacker who can control the properties object passed to a generated protobufjs message constructor or creation helper may be able to modify the prototype chain of the resulting message instance.
This is a per-instance prototype injection issue. It does not pollute Object.prototype or other global prototypes. The impact depends on downstream application behavior, such as relying on inherited properties, prototype methods, or instanceof checks for message objects.
Applications that only decode binary protobuf data, or that construct messages from trusted application-defined objects, are not directly affected by this issue.
Preconditions
- The application must allow an attacker to control or influence a plain object used to construct a protobufjs message.
- The object must contain an own enumerable
__proto__property, for example from parsed JSON input. - The application must pass that object to a generated message constructor or creation helper that copies arbitrary enumerable properties.
Workarounds
Do not pass attacker-controlled plain objects directly to generated message constructors with affected versions. If untrusted JSON input must be accepted, validate or sanitize object keys before constructing messages, and reject __proto__ properties.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | protobufjs | all versions | 7.5.6npm install protobufjs@7.5.6 |
| 📦npm | protobufjs | ≥ 8.0.0&&< 8.0.2 | 8.0.2npm install protobufjs@8.0.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for protobufjs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update protobufjs to 7.5.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44292 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-44292 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-44292. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-44292 in your dependencies?
O3 Security finds CVE-2026-44292 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.