CVE-2021-3578Network attack vector

Remote code execution via unexpected APPENDUID cast

Published Feb 16, 2022 · Updated Aug 3, 2024

Incorrect type conversion in Isync Project isync before 1.3.6 and 1.4.0 through 1.4.1 allows remote attackers to execute code. An unexpected APPENDUID response is cast to the wrong IMAP command subtype, causing a server-controlled integer to overwrite a pointer, allocator metadata, or the next heap allocation. The client must synchronize with a malicious or compromised IMAP server, which can turn the out-of-bounds write into code execution.

CVSS severity7.8
High
EPSS probability1.04%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect type conversion in Isync Project isync before 1.3.6 and 1.4.0 through 1.4.1 allows remote attackers to execute code. An unexpected APPENDUID response is cast to the wrong IMAP command subtype, causing a server-controlled integer to overwrite a pointer, allocator metadata, or the next heap allocation. The client must synchronize with a malicious or compromised IMAP server, which can turn the out-of-bounds write into code execution.

The record

CVE
CVE-2021-3578
Published
Feb 16, 2022
Updated
Aug 3, 2024
Vendor
Isync Project
Product
isync
Classifications
CWE-704, T1203
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Feb 16, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=isync 1.3.6, isync 1.4.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

Isync Project · isyncversion=isync 1.3.6, isync 1.4.2

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.2NIST NVDAV:L/AC:L/Au:N/C:C/I:C/A:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-704Incorrect Type Conversion or Cast
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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