{"id":"CVE-2026-59876","summary":"protobufjs: Text Format string map parsing can mutate returned map object prototype","details":"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.","aliases":["GHSA-jfj6-75fj-8934"],"modified":"2026-07-12T03:54:59.094750736Z","published":"2026-07-08T15:31:11.421Z","database_specific":{"cwe_ids":["CWE-1321"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59876.json","cna_assigner":"GitHub_M"},"references":[{"type":"WEB","url":"https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.6.5"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59876.json"},{"type":"ADVISORY","url":"https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-jfj6-75fj-8934"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59876"},{"type":"FIX","url":"https://github.com/protobufjs/protobuf.js/commit/9f97fe413072d3beb52c74e62d88ea8adc9444d8"},{"type":"FIX","url":"https://github.com/protobufjs/protobuf.js/pull/2335"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/protobufjs/protobuf.js","events":[{"introduced":"f8d5f3fe7104fade45407341228f0f0bb623e76d"},{"fixed":"9f97fe413072d3beb52c74e62d88ea8adc9444d8"},{"fixed":"3f7b2fa2dd679f7099a30098a75bcd776615e86f"}],"database_specific":{"extracted_events":[{"introduced":"8.2.0"},{"fixed":"8.6.5"}],"source":["AFFECTED_FIELD","REFERENCES"]}}],"versions":["protobufjs-v8.6.4","protobufjs-cli-v2.5.5","protobufjs-v8.6.3","protobufjs-cli-v2.5.4","protobufjs-v8.6.2","protobufjs-cli-v2.5.3","protobufjs-v8.6.1","protobufjs-cli-v2.5.2","protobufjs-v8.6.0","protobufjs-cli-v2.5.1","protobufjs-v8.5.0","protobufjs-cli-v2.5.0","protobufjs-v8.4.2","protobufjs-cli-v2.4.2","protobufjs-v8.4.1","protobufjs-cli-v2.4.1","protobufjs-v8.4.0","protobufjs-cli-v2.4.0","protobufjs-v8.3.0","protobufjs-cli-v2.3.0","protobufjs-v8.2.1","protobufjs-cli-v2.2.1","protobufjs-v8.2.0","protobufjs-cli-v2.2.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-59876.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N"}]}