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CVE-2026-44291 is a code injection vulnerability in protobufjs affecting versions through 7.5.5 and versions 8.0.0–8.0.1. Internal type lookup tables used to generate encoder and decoder functions are plain objects with inherited prototypes. When Object.prototype has already been polluted, inherited attacker-controlled properties can be mistaken for valid protobuf type information. Attacker-controlled strings can consequently be inserted into generated JavaScript and compiled with Function(), potentially enabling arbitrary JavaScript execution inside the Node.js process. This vulnerability is a code-generation gadget that depends on preexisting prototype pollution, rather than independently establishing that pollution.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository is a small standalone Python proof-of-concept for CVE-2026-44289, with the README also listing related CVEs affecting protobuf.js. The repository contains 6 files: a README, license, requirements, a CVE naming template, and one executable Python PoC file. The main and only code file, cve-2026-44289.py, implements a simplified recursive protobuf decoder class and a payload generator. Core capability: the PoC creates a deeply nested length-delimited protobuf-style payload using generate_deep_nested_payload(), then feeds it into VulnerableProtobufDecoder.decode(), which recursively decodes nested messages without a depth limit when run in vulnerable mode. This demonstrates uncontrolled recursion leading to RecursionError / simulated stack overflow, i.e., a denial-of-service condition. In safe mode, the same decoder is instantiated with a max_depth limit to show how the issue can be mitigated. Exploit structure: - VulnerableProtobufDecoder.decode(): recursively parses varint tags and length-delimited nested fields; the recursive self.decode(nested_data, depth + 1) call is the vulnerable behavior. - generate_deep_nested_payload(depth): constructs attacker-controlled nested binary input by repeatedly wrapping the previous payload in field 1, wire type 2. - _encode_varint(value): helper for protobuf-style varint encoding. - main(): CLI interface supporting payload generation and decode testing. Operationally, this is not a remote exploit and contains no shell, command execution, callback, or persistence logic. It is a local PoC / lab demonstrator for parser denial of service. No network services, IPs, or C2 endpoints are present. The only fingerprintable runtime artifact is the default payload file path payload.bin. The requirements file mentions protobuf and google-api-python-client, but the PoC itself relies only on Python standard library modules (argparse, sys, struct, typing). Overall, the repository’s purpose is educational demonstration of uncontrolled recursion in protobuf decoding rather than weaponized exploitation.
9 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A vulnerability in protobufjs versions prior to 7.5.6 and 8.0.2 allows previously polluted Object.prototype properties to influence internal type lookup tables used by generated encode and decode functions. This can inject attacker-controlled strings into generated JavaScript. Exploitation requires preexisting prototype pollution. The reference assigns a CVSS v3 base score of 8.1.
A protobufjs arbitrary code execution vulnerability caused by prototype pollution.
High-severity code injection vulnerability via prototype pollution in protobufjs that can, under certain conditions, inject attacker-controlled code into JavaScript generated by the library.
The most severe protobuf.js flaw, enabling arbitrary JavaScript execution in a Node.js process when attacker-controlled input reaches a prototype pollution gadget and protobuf.js compiles attacker-influenced generated code with Function().
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