CVE-2021-44143
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.
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
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 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS 2.0
- 7.5 High
AV: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 Critical
CVSS: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 Critical
CVSS: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 Critical
CVSS: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 Critical
CVSS: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 Critical
CVSS: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
| Package | Affected | Fixed |
|---|---|---|
isyncAlpine:v3.15 |
1.4.0 up to 1.4.4-r0 | 1.4.4-r0 |
isyncAlpine:v3.16 |
1.4.0 up to 1.4.4-r0 | 1.4.4-r0 |
isyncAlpine:v3.17 |
1.4.0 up to 1.4.4-r0 | 1.4.4-r0 |
isyncAlpine:v3.18 |
1.4.0 up to 1.4.4-r0 | 1.4.4-r0 |
isyncAlpine:v3.19 |
1.4.0 up to 1.4.4-r0 | 1.4.4-r0 |
isyncAlpine:v3.20 |
1.4.0 up to 1.4.4-r0 | 1.4.4-r0 |
isyncAlpine:v3.21 |
1.4.0 up to 1.4.4-r0 | 1.4.4-r0 |
isyncAlpine:v3.22 |
1.4.0 up to 1.4.4-r0 | 1.4.4-r0 |
isyncAlpine:v3.23 |
1.4.0 up to 1.4.4-r0 | 1.4.4-r0 |
isyncAlpine:v3.24 |
1.4.0 up to 1.4.4-r0 | 1.4.4-r0 |
Show 10 moreShow less
| Package | Affected | Fixed |
|---|---|---|
isyncDebian:12 |
before 1.4.4-1 | 1.4.4-1 |
isyncDebian:13 |
before 1.4.4-1 | 1.4.4-1 |
isyncDebian:14 |
before 1.4.4-1 | 1.4.4-1 |
isyncUbuntu:16.04:LTS |
All versions, plus listed versions 1.1.2-1 |
None known |
isyncUbuntu: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 |
isyncUbuntu:24.04:LTS |
All versions, plus listed versions 1.4.4-51.4.4-5build21.4.4-5build3 |
None known |
isyncUbuntu:25.10 |
All versions, plus listed versions 1.4.4-5build31.5.1-1ubuntu1 |
None known |
isyncUbuntu:26.10 |
All versions, plus listed versions 1.5.1-1ubuntu21.5.1-1ubuntu4 |
None known |
isyncUbuntu:26.04:LTS |
All versions, plus listed versions 1.5.1-1ubuntu11.5.1-1ubuntu2 |
None known |
isyncopenSUSE:Tumbleweed From an advisory covering 2 CVEs |
before 1.4.4-1.1 | 1.4.4-1.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| affected, aliases, references | OSV | |
| aliases | EUVD | |
| first indexed | CVE 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
bugs.debian.org/cgi-bin/bugreport.cgi?bug=999804
sourceforge.net/p/isync/isync/ref/master/tags
sourceforge.net/p/isync/isync/commit_browser
openwall.com/lists/oss-security/2021/12/03/2
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CYZ2GNB4ZO2T27D2XNUWMCS3THZYSJQU
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LCBSY7OZ57XNC6ZYXF6WU5KBSWITZVDX
Show 11 moreShow less
security.gentoo.org/glsa/202208-15
nvd.nist.gov/vuln/detail/CVE-2021-44143
lists.fedoraproject.org/archives/list/[email protected]/message/CYZ2GNB4ZO2T27D2XNUWMCS3THZYSJQU
lists.fedoraproject.org/archives/list/[email protected]/message/LCBSY7OZ57XNC6ZYXF6WU5KBSWITZVDX
github.com/advisories/GHSA-2h85-c54w-28vc
security.alpinelinux.org/vuln/CVE-2021-44143
security-tracker.debian.org/tracker/CVE-2021-44143
ubuntu.com/security/CVE-2021-44143
cve.org/CVERecord?id=CVE-2021-44143
suse.com/security/cve/CVE-2021-3657
suse.com/security/cve/CVE-2021-44143