CVE-2026-44288 — protobufjs
MEDIUMCVE-2026-44288 is a medium-severity (CVSS 5.3) CWE-176 vulnerability in protobufjs. A fix is available for protobufjs — see the affected versions and patch details below.
protobufjs: Overlong UTF-8 decoding
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-2026-44288.
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-2026-44288 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 379,145 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.
protobufjsnpm@protobufjs/utf8npmDescription
Summary
protobufjs includes a minimal UTF-8 decoder used in non-Node and fallback decoding paths. The affected decoder accepted overlong UTF-8 byte sequences and decoded them to their canonical characters instead of replacing them.
The issue concerns overlong encodings and code points outside the Unicode range. protobufjs may still accept some non-strict UTF-8 input for compatibility, so applications should not rely on protobufjs as a general-purpose strict UTF-8 validator.
Impact
An attacker who can provide protobuf binary data decoded through the affected UTF-8 path may be able to bypass application-level checks that inspect raw bytes before protobuf string decoding. For example, bytes that do not contain certain ASCII characters could decode to strings containing those characters.
The practical impact depends on downstream application validation and how decoded strings are used. Node.js Buffer-backed decoding paths are not directly affected when they use Node's native UTF-8 decoding.
Preconditions
- The application must decode protobuf binary data influenced by an attacker.
- The affected protobuf string field must be decoded through protobufjs's minimal UTF-8 decoder rather than a native UTF-8 decoder.
- The application must rely on byte-level filtering or validation before protobuf string decoding.
- The decoded string must then be used in a security-sensitive context.
Workarounds
Avoid relying only on byte-level filtering before protobuf string decoding with affected versions. Validate decoded strings at the point where they are used, and prefer runtime paths that use native UTF-8 decoding where necessary.
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 |
| 📦npm | @protobufjs/utf8 | all versions | 1.1.1npm install @protobufjs/utf8@1.1.1 |
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-2026-44288 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-2026-44288 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-44288. 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-2026-44288 in your dependencies?
O3 Security finds CVE-2026-44288 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.