{"cve":"CVE-2020-6820","nvd":{"published":"2020-04-24T16:15:13.463","modified":"2026-06-17T03:23:51.990","status":"Analyzed","description":"Under certain conditions, when handling a ReadableStream, a race condition can cause a use-after-free. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Thunderbird < 68.7.0, Firefox < 74.0.1, and Firefox ESR < 68.6.1.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","score":8.1},"cwes":["CWE-362"],"references":["https://bugzilla.mozilla.org/show_bug.cgi?id=1626728","https://usn.ubuntu.com/4335-1/","https://www.mozilla.org/security/advisories/mfsa2020-11/","https://www.mozilla.org/security/advisories/mfsa2020-14/","https://bugzilla.mozilla.org/show_bug.cgi?id=1626728"],"products":["mozilla:firefox","mozilla:thunderbird"],"source":"nvd","synced_at":"2026-10-19T21:04:18.695612450+00:00"},"epss":{"cve":"CVE-2020-6820","score":0.07063,"percentile":0.94209,"date":"2026-11-01"},"kev":{"cve":"CVE-2020-6820","date_added":"2021-11-03","due_date":"2022-05-03","vendor":"Mozilla","product":"Firefox and Thunderbird","known_ransomware":false},"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}