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
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
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 |
Affected Products
protobufjsprotobufjs_projectDetection & 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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Moderate: A flaw in protobufjs, as used in Red Hat products, allows an attacker to bypass application-level security checks. By providing specially crafted protobuf binary data with overlong UTF-8 sequences, an attacker could cause incorrect data interpretation, potentially circumventing security controls that inspect…
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.Source: Red Hat security advisory for CVE-2026-44288 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-44288 in your dependencies?
Find it across npm, including transitive dependencies.