{"id":"CVE-2026-123561","aliases":["EUVD-2026-119446","GHSA-2fcf-p6fg-p2wf"],"status":"published","title":"Sveltejs devalue before 5.9.3 __proto__ Rejection Bypass via Property-Key Coercion","description":"devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__ rejection through property-key coercion, an incomplete fix for GHSA-mwv9-gp5h-frr4. Attackers can supply crafted payloads that yield objects with a __proto__ own property, which alone does not cause prototype pollution.","severity":{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00249,"percentile":0.16345,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-1321"],"published":"2026-11-08T01:38:01Z","modified":"2026-11-08T10:45:32Z","products":[{"vendor":"sveltejs","product":"devalue"}],"references":[{"url":"https://github.com/sveltejs/devalue/security/advisories/GHSA-4q55-j62x-fr9h","tags":["vendor-advisory","advisory"]},{"url":"https://www.vulncheck.com/advisories/sveltejs-devalue-before-5.9.3-proto-rejection-bypass-via-property-key-coercion","tags":["third-party-advisory","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-123561","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-2fcf-p6fg-p2wf"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/123xxx/CVE-2026-123561.json","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-123561","title":"Sveltejs devalue before 5.9.3 __proto__ Rejection Bypass via Property-Key Coercion","description":"devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__ rejection through property-key coercion, an incomplete fix for GHSA-mwv9-gp5h-frr4. Attackers can supply crafted payloads that yield objects with a __proto__ own property, which alone does not cause prototype pollution.","status":"published","published":"2026-11-08T01:38:01.726Z","modified":"2026-11-10T17:58:35.941Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna"},{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"low","assessor":"cna"}],"cwes":["CWE-1321"],"updated_at":"2026-11-08T02:36:49.037074Z"}],"euvd":[{"id":"EUVD-2026-119446","description":"devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__ rejection through property-key coercion, an incomplete fix for GHSA-mwv9-gp5h-frr4. Attackers can supply crafted payloads that yield objects with a __proto__ own property, which alone does not cause prototype pollution.","status":"published","published":"2026-11-08T01:38:01Z","modified":"2026-11-10T17:58:35Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-08T06:12:04.782489Z"}],"ghsa":[{"id":"GHSA-2fcf-p6fg-p2wf","title":"devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__...","description":"devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__ rejection through property-key coercion, an incomplete fix for GHSA-mwv9-gp5h-frr4. Attackers can supply crafted payloads that yield objects with a __proto__ own property, which alone does not cause prototype pollution.","status":"published","published":"2026-11-08T03:30:33Z","modified":"2026-11-08T03:30:39Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium"},{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"low"}],"cwes":["CWE-1321"],"updated_at":"2026-11-08T03:41:53.166172Z"}],"nvd":[{"id":"CVE-2026-123561","description":"devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__ rejection through property-key coercion, an incomplete fix for GHSA-mwv9-gp5h-frr4. Attackers can supply crafted payloads that yield objects with a __proto__ own property, which alone does not cause prototype pollution.","status":"published","published":"2026-11-08T02:16:48.4Z","modified":"2026-11-12T20:28:31.817Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium","assessor":"secondary"},{"version":"3.1","score":3.7,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"low","assessor":"secondary"}],"cwes":["CWE-1321"],"updated_at":"2026-11-10T20:21:08.995077Z"}],"osv":[{"id":"CVE-2026-123561","title":"Sveltejs devalue before 5.9.3 __proto__ Rejection Bypass via Property-Key Coercion","description":"devalue before 5.9.3 allows malformed null-prototype object keys to bypass parse's __proto__ rejection through property-key coercion, an incomplete fix for GHSA-mwv9-gp5h-frr4. Attackers can supply crafted payloads that yield objects with a __proto__ own property, which alone does not cause prototype pollution.","status":"published","published":"2026-11-08T01:38:01.726Z","modified":"2026-11-12T02:31:03.746212782Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-1321"],"updated_at":"2026-11-08T11:04:05.022583Z"}]}}