CVE-2021-38371
The STARTTLS feature in Exim through 4.94.2 allows response injection (buffering) during MTA SMTP...
7.5 HighFix available
The STARTTLS feature in Exim through 4.94.2 allows response injection (buffering) during MTA SMTP sending.
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
- None
- Integrity
- High
- Availability
- None
Exploit likelihood
2.00%Up 1.2 points since Aug 11, 2021
What each source reports
NVD Score used
The STARTTLS feature in Exim through 4.94.2 allows response injection (buffering) during MTA SMTP sending.
- Record
CVE-2021-38371- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - CVSS 2.0
- 5.0 Medium
AV:N/AC:L/Au:N/C:N/I:P/A:N - Weakness
- CWE-74
- Updated
- 2026-11-02
CVE List No score
The STARTTLS feature in Exim through 4.94.2 allows response injection (buffering) during MTA SMTP sending.
- Record
CVE-2021-38371- Updated
- 2026-11-02
EUVDEUVD-2021-24824 No score
The STARTTLS feature in Exim through 4.94.2 allows response injection (buffering) during MTA SMTP sending.
- Record
EUVD-2021-24824- Updated
- 2026-11-02
GitHub AdvisoriesGHSA-8gh2-336j-g8v7
The STARTTLS feature in Exim through 4.94.2 allows response injection (buffering) during MTA SMTP...
The STARTTLS feature in Exim through 4.94.2 allows response injection (buffering) during MTA SMTP sending.
- Record
GHSA-8gh2-336j-g8v7- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Weakness
- CWE-74
- Updated
- 2026-11-02
OSV
The STARTTLS feature in Exim through 4.94.2 allows response injection (buffering) during MTA SMTP sending.
- Record
CVE-2021-38371- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Updated
- 2026-11-02
OSVDEBIAN-CVE-2021-38371
The STARTTLS feature in Exim through 4.94.2 allows response injection (buffering) during MTA SMTP sending.
- Record
DEBIAN-CVE-2021-38371- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Updated
- 2026-11-02
Show 6 moreShow less
OSVUBUNTU-CVE-2021-38371
The STARTTLS feature in Exim through 4.94.2 allows response injection (buffering) during MTA SMTP sending.
- Record
UBUNTU-CVE-2021-38371- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N - Updated
- 2026-11-02
OSVCLSA-2023-1687794906 No score
exim: Fix of CVE-2021-38371
- CVE-2021-38371: Enforce STARTTLS sync point, client side in src/transports/smtp.c
- Record
CLSA-2023-1687794906- Updated
- 2026-11-02
OSVCLSA-2023-1687795205 No score
exim: Fix of CVE-2021-38371
- CVE-2021-38371: Enforce STARTTLS sync point, client side in src/transports/smtp.c
- Record
CLSA-2023-1687795205- Updated
- 2026-11-02
OSVCLSA-2023-1687795531 No score
Fix CVE(s): CVE-2021-38371
- SECURITY UPDATE: Response injection (buffering) during MTA SMTP sending
- debian/patches/CVE-2021-38371.patch: Enforce STARTTLS sync point, client side in src/transports/smtp.c
- CVE-2021-38371
- Record
CLSA-2023-1687795531- Updated
- 2026-11-02
OSVCLSA-2023-1688070370 No score
Fix CVE(s): CVE-2021-38371
- SECURITY UPDATE: Response injection (buffering) during MTA SMTP sending
- debian/patches/CVE-2021-38371.patch: Enforce STARTTLS sync point, client side in src/transports/smtp.c
- CVE-2021-38371
- Record
CLSA-2023-1688070370- Updated
- 2026-11-02
OSVUSN-6881-1 No score
exim4 vulnerability
It was discovered that Exim did not enforce STARTTLS sync point on client side. An attacker could possibly use this issue to perform response injection during MTA SMTP sending.
- Record
USN-6881-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
eximTuxCare:CentOS:6 |
before 4.92.3-3.el6.tuxcare.els3 | 4.92.3-3.el6.tuxcare.els3 |
exim-greylistTuxCare:CentOS:6 |
before 4.92.3-3.el6.tuxcare.els3 | 4.92.3-3.el6.tuxcare.els3 |
exim-monTuxCare:CentOS:6 |
before 4.92.3-3.el6.tuxcare.els3 | 4.92.3-3.el6.tuxcare.els3 |
exim-mysqlTuxCare:CentOS:6 |
before 4.92.3-3.el6.tuxcare.els3 | 4.92.3-3.el6.tuxcare.els3 |
exim-pgsqlTuxCare:CentOS:6 |
before 4.92.3-3.el6.tuxcare.els3 | 4.92.3-3.el6.tuxcare.els3 |
eximTuxCare:OracleLinux:6 |
before 4.92.3-3.el6.tuxcare.els3 | 4.92.3-3.el6.tuxcare.els3 |
exim-greylistTuxCare:OracleLinux:6 |
before 4.92.3-3.el6.tuxcare.els3 | 4.92.3-3.el6.tuxcare.els3 |
exim-monTuxCare:OracleLinux:6 |
before 4.92.3-3.el6.tuxcare.els3 | 4.92.3-3.el6.tuxcare.els3 |
exim-mysqlTuxCare:OracleLinux:6 |
before 4.92.3-3.el6.tuxcare.els3 | 4.92.3-3.el6.tuxcare.els3 |
exim-pgsqlTuxCare:OracleLinux:6 |
before 4.92.3-3.el6.tuxcare.els3 | 4.92.3-3.el6.tuxcare.els3 |
Show 22 moreShow less
| Package | Affected | Fixed |
|---|---|---|
exim4TuxCare:Ubuntu:18.04 |
before 4.90.1-1ubuntu1.10+tuxcare.els1 | 4.90.1-1ubuntu1.10+tuxcare.els1 |
exim4-baseTuxCare:Ubuntu:18.04 |
before 4.90.1-1ubuntu1.10+tuxcare.els1 | 4.90.1-1ubuntu1.10+tuxcare.els1 |
exim4-configTuxCare:Ubuntu:18.04 |
before 4.90.1-1ubuntu1.10+tuxcare.els1 | 4.90.1-1ubuntu1.10+tuxcare.els1 |
exim4-daemon-heavyTuxCare:Ubuntu:18.04 |
before 4.90.1-1ubuntu1.10+tuxcare.els1 | 4.90.1-1ubuntu1.10+tuxcare.els1 |
exim4-daemon-lightTuxCare:Ubuntu:18.04 |
before 4.90.1-1ubuntu1.10+tuxcare.els1 | 4.90.1-1ubuntu1.10+tuxcare.els1 |
exim4-devTuxCare:Ubuntu:18.04 |
before 4.90.1-1ubuntu1.10+tuxcare.els1 | 4.90.1-1ubuntu1.10+tuxcare.els1 |
eximon4TuxCare:Ubuntu:18.04 |
before 4.90.1-1ubuntu1.10+tuxcare.els1 | 4.90.1-1ubuntu1.10+tuxcare.els1 |
exim4TuxCare:Ubuntu:16.04 |
before 4.86.2-2ubuntu2.6+tuxcare.els3 | 4.86.2-2ubuntu2.6+tuxcare.els3 |
exim4-baseTuxCare:Ubuntu:16.04 |
before 4.86.2-2ubuntu2.6+tuxcare.els3 | 4.86.2-2ubuntu2.6+tuxcare.els3 |
exim4-configTuxCare:Ubuntu:16.04 |
before 4.86.2-2ubuntu2.6+tuxcare.els3 | 4.86.2-2ubuntu2.6+tuxcare.els3 |
exim4-daemon-heavyTuxCare:Ubuntu:16.04 |
before 4.86.2-2ubuntu2.6+tuxcare.els3 | 4.86.2-2ubuntu2.6+tuxcare.els3 |
exim4-daemon-lightTuxCare:Ubuntu:16.04 |
before 4.86.2-2ubuntu2.6+tuxcare.els3 | 4.86.2-2ubuntu2.6+tuxcare.els3 |
exim4-devTuxCare:Ubuntu:16.04 |
before 4.86.2-2ubuntu2.6+tuxcare.els3 | 4.86.2-2ubuntu2.6+tuxcare.els3 |
eximon4TuxCare:Ubuntu:16.04 |
before 4.86.2-2ubuntu2.6+tuxcare.els3 | 4.86.2-2ubuntu2.6+tuxcare.els3 |
exim4Debian:12 |
before 4.95~RC2-1 | 4.95~RC2-1 |
exim4Debian:13 |
before 4.95~RC2-1 | 4.95~RC2-1 |
exim4Debian:14 |
before 4.95~RC2-1 | 4.95~RC2-1 |
exim4Debian:11 |
before 4.94.2-7+deb11u4, plus listed versions 4.94.2-74.94.2-7+deb11u14.94.2-7+deb11u24.94.2-7+deb11u3 |
4.94.2-7+deb11u4 |
exim4Ubuntu:Pro:14.04:LTS |
before 4.82-3ubuntu2.4+esm8, plus listed versions 4.80-7ubuntu34.80-7ubuntu44.80-9ubuntu14.80-9ubuntu24.82-3ubuntu1 Show 11 moreShow less4.82-3ubuntu24.82-3ubuntu2.14.82-3ubuntu2.24.82-3ubuntu2.34.82-3ubuntu2.44.82-3ubuntu2.4+esm14.82-3ubuntu2.4+esm24.82-3ubuntu2.4+esm34.82-3ubuntu2.4+esm44.82-3ubuntu2.4+esm64.82-3ubuntu2.4+esm7 |
4.82-3ubuntu2.4+esm8 |
exim4Ubuntu:Pro:16.04:LTS |
before 4.86.2-2ubuntu2.6+esm7, plus listed versions 4.86-3ubuntu14.86-7ubuntu14.86-7ubuntu24.86-7ubuntu34.86.2-2ubuntu1 Show 12 moreShow less4.86.2-2ubuntu24.86.2-2ubuntu2.14.86.2-2ubuntu2.24.86.2-2ubuntu2.34.86.2-2ubuntu2.44.86.2-2ubuntu2.54.86.2-2ubuntu2.64.86.2-2ubuntu2.6+esm14.86.2-2ubuntu2.6+esm24.86.2-2ubuntu2.6+esm44.86.2-2ubuntu2.6+esm54.86.2-2ubuntu2.6+esm6 |
4.86.2-2ubuntu2.6+esm7 |
exim4Ubuntu:Pro:18.04:LTS |
before 4.90.1-1ubuntu1.10+esm4, plus listed versions 4.89-5ubuntu14.89-9ubuntu14.89-9ubuntu24.89-9ubuntu34.89-9ubuntu4 Show 12 moreShow less4.90.1-1ubuntu14.90.1-1ubuntu1.14.90.1-1ubuntu1.24.90.1-1ubuntu1.34.90.1-1ubuntu1.44.90.1-1ubuntu1.54.90.1-1ubuntu1.84.90.1-1ubuntu1.94.90.1-1ubuntu1.104.90.1-1ubuntu1.10+esm14.90.1-1ubuntu1.10+esm24.90.1-1ubuntu1.10+esm3 |
4.90.1-1ubuntu1.10+esm4 |
exim4Ubuntu:20.04:LTS |
before 4.93-13ubuntu1.11, plus listed versions 4.92.1-1ubuntu34.92.1-1ubuntu44.93~RC2-1ubuntu14.93-9ubuntu14.93-11ubuntu1 Show 9 moreShow less4.93-12ubuntu14.93-13ubuntu14.93-13ubuntu1.14.93-13ubuntu1.54.93-13ubuntu1.64.93-13ubuntu1.74.93-13ubuntu1.84.93-13ubuntu1.94.93-13ubuntu1.10 |
4.93-13ubuntu1.11 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-38371 is a high vulnerability (CVSS 7.5) in Exim, published August 10, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.00%, the 80th percentile. Fixed in exim 4.92.3-3.el6.tuxcare.els3.
References
nostarttls.secvuln.info
exim.org
lists.debian.org/debian-lts-announce/2024/10/msg00029.html
nvd.nist.gov/vuln/detail/CVE-2021-38371
github.com/advisories/GHSA-8gh2-336j-g8v7
Show 8 moreShow less
errata.cloudlinux.com/els6/CLSA-2023-1687794906.html
security-tracker.debian.org/tracker/CVE-2021-38371
ubuntu.com/security/CVE-2021-38371
cve.org/CVERecord?id=CVE-2021-38371