CVE-2021-20247: debian debian_linux Improper Input Validation
Vulnerability summary
CVE-2021-20247 is a high (CVSS 7.4) Improper Input Validation vulnerability in debian debian_linux. EPSS estimates a 1.88% chance of exploitation in the next 30 days, higher than 79.1% of scored vulnerabilities. 1 public exploit is recorded.
Advisory lineage
Upstream 0 · Downstream 2 · Related 1Timeline
- 23-02-2021PublishedVulnerability first disclosed.
- 03-08-2024Last modifiedVulnerability information updated.
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 metrics
4 scores · 3 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated7.4HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- OSV · DebianEcosystem advisory · calculated7.4HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS trend
Probability
1.88%
Chance of exploitation in the next 30 days
Percentile
79%
Versus all other CVEs
30-day change
0.00 pp
From 1.88% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
1 foundExploit Reference (openwall.com)
Maturity: unknown
Weaknesses
CWE · root cause- CWE-20Improper Input ValidationThe product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
- CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
Affected systems
Debian2 products
- isync< 1.3.0-2.1
- debian_linuxEOL9.0
Fedoraproject2 products
- extra_packages_for_enterprise_linux8.0
- fedoraEOL32 | 33
Mbsync_project1 product
- mbsync< 1.3.5 | ≥ 1.4.0, < 1.4.1
Opensuse1 product
- isync&distro=openSUSE Leap 15.2< 1.3.5-lp152.4.3.1
Suse1 product
- isync&distro=SUSE Package Hub 15 SP2< 1.3.5-bp152.4.3.1
Ubuntu1 product
- isyncAll versions (No fix recorded)
6 vendors · 8 products
References
13 links- www.openwall.com/lists/oss-security/2021/02/22/1X Refsource MISCREPORTExploitMailing ListThird Party Advisory
lists.debian.org/debian-lts-announce/2022/07/msg00001.htmlMailing ListX Refsource MLISTThird Party Advisory- lists.opensuse.org/archives/…Advisory
Show all 13 references
- lists.opensuse.org/archives/…Advisory