There are packages installed that are affected by multiple vulnerabilities referenced in the following CVEs:

  - A flaw was found in mbsync versions prior to 1.4.4. Due to inadequate handling of extremely large (>=2GiB)
    IMAP literals, malicious or compromised IMAP servers, and hypothetically even external email senders,
    could cause several different buffer overflows, which could conceivably be exploited for remote code
    execution. (CVE-2021-3657)

  - A flaw was found in mbsync in isync 1.4.0 through 1.4.3. Due to an unchecked condition, a malicious or
    compromised IMAP server could use a crafted mail message that lacks headers (i.e., one that starts with an
    empty line) to provoke a heap overflow, which could conceivably be exploited for remote code execution.
    (CVE-2021-44143)

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - A flaw was found in mbsync versions prior to 1.4.4. Due to inadequate handling of extremely large (>=2GiB)     IMAP literals, malicious or compromised IMAP servers, and hypothetically even external email senders,     could cause several different buffer overflows, which could conceivably be exploited for remote code     execution. (CVE-2021-3657)

Note that Nessus relies on the presence of the package as reported by the vendor.

The remote Debian 9 host has a package installed that is affected by multiple vulnerabilities as referenced in the dla-3066 advisory.

  - 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. (CVE-2021-20247)

  - A flaw was found in mbsync before v1.3.6 and v1.4.2, where an unchecked pointer cast allows a malicious or     compromised server to write an arbitrary integer value past the end of a heap-allocated structure by     issuing an unexpected APPENDUID response. This could be plausibly exploited for remote code execution on     the client. (CVE-2021-3578)

  - A flaw was found in mbsync versions prior to 1.4.4. Due to inadequate handling of extremely large (>=2GiB)     IMAP literals, malicious or compromised IMAP servers, and hypothetically even external email senders,     could cause several different buffer overflows, which could conceivably be exploited for remote code     execution. (CVE-2021-3657)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote host is affected by the vulnerability described in GLSA-202208-15 (isync: Multiple Vulnerabilities)

  - 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. (CVE-2021-20247)

  - A flaw was found in mbsync before v1.3.6 and v1.4.2, where an unchecked pointer cast allows a malicious or     compromised server to write an arbitrary integer value past the end of a heap-allocated structure by     issuing an unexpected APPENDUID response. This could be plausibly exploited for remote code execution on     the client. (CVE-2021-3578)

  - A flaw was found in mbsync versions prior to 1.4.4. Due to inadequate handling of extremely large (>=2GiB)     IMAP literals, malicious or compromised IMAP servers, and hypothetically even external email senders,     could cause several different buffer overflows, which could conceivably be exploited for remote code     execution. (CVE-2021-3657)

  - A flaw was found in mbsync in isync 1.4.0 through 1.4.3. Due to an unchecked condition, a malicious or     compromised IMAP server could use a crafted mail message that lacks headers (i.e., one that starts with an     empty line) to provoke a heap overflow, which could conceivably be exploited for remote code execution.
    (CVE-2021-44143)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Published	Updated	Severity
405024	Alpine: multiple isync packages: security update to 1.4.4-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	10/31/2023	7/2/2026	critical
427616	Alpine: multiple isync packages: security update to 1.4.4-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	5/16/2025	12/11/2025	critical
405024	Alpine: multiple isync packages: security update to 1.4.4-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	10/31/2023	7/2/2026	critical
427616	Alpine: multiple isync packages: security update to 1.4.4-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	5/16/2025	12/11/2025	critical
255744	Linux Distros Unpatched Vulnerability : CVE-2021-3657	Nessus	Misc.	8/27/2025	9/2/2026	critical
162682	Debian DLA-3066-1 : isync - LTS security update	Nessus	Debian Local Security Checks	7/1/2022	10/19/2023	critical
164046	GLSA-202208-15 : isync: Multiple Vulnerabilities	Nessus	Gentoo Local Security Checks	8/11/2022	10/16/2023	critical

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