{"cve":"CVE-2021-20247","nvd":{"published":"2021-02-23T19:15:13.510","modified":"2026-06-17T03:33:32.533","status":"Modified","description":"A flaw was found in mbsync before v1.3.5 and v1.4.1. Validations of the mailbox names returned by IMAP LIST/LSUB do not occur allowing a malicious or compromised server to use specially crafted mailbox names containing '..' path components to access data outside the designated mailbox on the opposite end of the synchronization channel. The highest threat from this vulnerability is to data confidentiality and integrity.","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:N","score":7.4},"cwes":["CWE-22","CWE-20"],"references":["https://bugzilla.redhat.com/show_bug.cgi?id=1928963","https://lists.debian.org/debian-lts-announce/2022/07/msg00001.html","https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CAXQLCK35QGRCRENRTGKJO4VVZGUXUJJ/","https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GVDEBZQJMWDW5JFK4NTHH6DAFNAZTESW/","https://security.gentoo.org/glsa/202208-15"],"products":["debian:debian_linux","fedoraproject:extra_packages_for_enterprise_linux","fedoraproject:fedora","mbsync_project:mbsync"],"source":"nvd","synced_at":"2026-10-19T21:15:50.279857260+00:00"},"epss":{"cve":"CVE-2021-20247","score":0.0188,"percentile":0.79451,"date":"2026-10-31"},"kev":null,"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."]}