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CVE-2021-44143

A flaw was found in mbsync in isync 1.4.0 through 1.4.3. Due to an unchecked condition, a...

9.8 CriticalFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

3.78%Up 2.0 points since Nov 23, 2021
90%50%10%1%

What each source reports

NVD Score used 9.8

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.

Record
CVE-2021-44143
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 2.0
7.5 HighAV:N/AC:L/Au:N/C:P/I:P/A:P
Weakness
CWE-787
Updated
2026-11-02
CVE List No score

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.

Record
CVE-2021-44143
Updated
2026-11-02
EUVDEUVD-2021-30996 No score

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.

Record
EUVD-2021-30996
Updated
2026-11-03
GitHub AdvisoriesGHSA-2h85-c54w-28vc 9.8

A flaw was found in mbsync in isync 1.4.0 through 1.4.3. Due to an unchecked condition, a...

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.

Record
GHSA-2h85-c54w-28vc
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness
CWE-787
Updated
2026-11-02
OSVALPINE-CVE-2021-44143 9.8

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.

Record
ALPINE-CVE-2021-44143
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-03
OSV 9.8

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.

Record
CVE-2021-44143
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVDEBIAN-CVE-2021-44143 9.8

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.

Record
DEBIAN-CVE-2021-44143
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2021-44143 9.8

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.

Record
UBUNTU-CVE-2021-44143
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVopenSUSE-SU-2024:11779-1 No score

isync-1.4.4-1.1 on GA media

These are all security issues fixed in the isync-1.4.4-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2024:11779-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
isync
Alpine:v3.15
1.4.0 up to 1.4.4-r0
1.4.4-r0
isync
Alpine:v3.16
1.4.0 up to 1.4.4-r0
1.4.4-r0
isync
Alpine:v3.17
1.4.0 up to 1.4.4-r0
1.4.4-r0
isync
Alpine:v3.18
1.4.0 up to 1.4.4-r0
1.4.4-r0
isync
Alpine:v3.19
1.4.0 up to 1.4.4-r0
1.4.4-r0
isync
Alpine:v3.20
1.4.0 up to 1.4.4-r0
1.4.4-r0
isync
Alpine:v3.21
1.4.0 up to 1.4.4-r0
1.4.4-r0
isync
Alpine:v3.22
1.4.0 up to 1.4.4-r0
1.4.4-r0
isync
Alpine:v3.23
1.4.0 up to 1.4.4-r0
1.4.4-r0
isync
Alpine:v3.24
1.4.0 up to 1.4.4-r0
1.4.4-r0
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Affected packages
PackageAffectedFixed
isync
Debian:12
before 1.4.4-1
1.4.4-1
isync
Debian:13
before 1.4.4-1
1.4.4-1
isync
Debian:14
before 1.4.4-1
1.4.4-1
isync
Ubuntu:16.04:LTS
All versions, plus listed versions
1.1.2-1
None known
isync
Ubuntu:22.04:LTS
All versions, plus listed versions
1.3.0-2.21.4.3-11.4.4-11.4.4-31.4.4-3ubuntu0.22.04.1
None known
isync
Ubuntu:24.04:LTS
All versions, plus listed versions
1.4.4-51.4.4-5build21.4.4-5build3
None known
isync
Ubuntu:25.10
All versions, plus listed versions
1.4.4-5build31.5.1-1ubuntu1
None known
isync
Ubuntu:26.10
All versions, plus listed versions
1.5.1-1ubuntu21.5.1-1ubuntu4
None known
isync
Ubuntu:26.04:LTS
All versions, plus listed versions
1.5.1-1ubuntu11.5.1-1ubuntu2
None known
isync
openSUSE:Tumbleweed
From an advisory covering 2 CVEs
before 1.4.4-1.1
1.4.4-1.1

History

History
RecordedChangedSources
affected, facts
affected, aliases, referencesOSV
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-44143 is a critical vulnerability (CVSS 9.8) in Isync Project Isync, published November 22, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 3.78%, the 90th percentile. Fixed in isync 1.4.4-r0.

References

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