Answer in brief
CVE-2026-59876 records a Medium severity (CVSS 4.8) vulnerability in protobufjs: Text Format string map parsing can mutate returned map object prototype. The current sources do not mark it as known exploited. The current feed maps protobufjs/protobuf.js (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 4.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps protobufjs/protobuf.js (generic). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:a:protobufjs_project:protobufjs:*:*:*:*:*:node.js:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| protobufjs/protobuf.jsgeneric | >=8.2.0 <8.6.5 | 8.6.5 |
Published upstream
Jul 8, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 25, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 8, 2026
protobufjs compiles protobuf definitions into JavaScript (JS) functions. From 8.2.0 until 8.6.5, the protobufjs Text Format extension parsed string-keyed map entries using ordinary property assignment, allowing a map entry with key __proto__ to change the prototype of the returned map object instead of creating an own map entry in protobufjs/ext/textformat. This issue is fixed in version 8.6.5.
Quoted source text, attributed separately from HOL analysis.