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CVE-2020-15953

LibEtPan through 1.9.4, as used in MailCore 2 through 0.6.3 and other products, has a STARTTLS...

7.4 HighFix available

LibEtPan through 1.9.4, as used in MailCore 2 through 0.6.3 and other products, has a STARTTLS buffering issue that affects IMAP, SMTP, and POP3. When a server sends a "begin TLS" response, the client reads additional data (e.g., from a meddler-in-the-middle attacker) and evaluates it in a TLS context, aka "response injection."

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
None

Exploit likelihood

2.40%Up 0.7 points since Apr 14, 2021
90%50%10%1%

What each source reports

NVD Score used 7.4

LibEtPan through 1.9.4, as used in MailCore 2 through 0.6.3 and other products, has a STARTTLS buffering issue that affects IMAP, SMTP, and POP3. When a server sends a "begin TLS" response, the client reads additional data (e.g., from a meddler-in-the-middle attacker) and evaluates it in a TLS context, aka "response injection."

Record
CVE-2020-15953
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS 2.0
5.8 MediumAV:N/AC:M/Au:N/C:P/I:P/A:N
Weakness
CWE-74
Updated
2026-11-02
CVE List No score

LibEtPan through 1.9.4, as used in MailCore 2 through 0.6.3 and other products, has a STARTTLS buffering issue that affects IMAP, SMTP, and POP3. When a server sends a "begin TLS" response, the client reads additional data (e.g., from a meddler-in-the-middle attacker) and evaluates it in a TLS context, aka "response injection."

Record
CVE-2020-15953
Updated
2026-11-02
EUVDEUVD-2020-7924 No score

LibEtPan through 1.9.4, as used in MailCore 2 through 0.6.3 and other products, has a STARTTLS buffering issue that affects IMAP, SMTP, and POP3. When a server sends a "begin TLS" response, the client reads additional data (e.g., from a meddler-in-the-middle attacker) and evaluates it in a TLS context, aka "response injection."

Record
EUVD-2020-7924
Updated
2026-11-03
GitHub AdvisoriesGHSA-f329-rp43-94r4 7.4

LibEtPan through 1.9.4, as used in MailCore 2 through 0.6.3 and other products, has a STARTTLS...

LibEtPan through 1.9.4, as used in MailCore 2 through 0.6.3 and other products, has a STARTTLS buffering issue that affects IMAP, SMTP, and POP3. When a server sends a "begin TLS" response, the client reads additional data (e.g., from a meddler-in-the-middle attacker) and evaluates it in a TLS context, aka "response injection."

Record
GHSA-f329-rp43-94r4
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-74
Updated
2026-11-02
OSVALPINE-CVE-2020-15953 7.4

LibEtPan through 1.9.4, as used in MailCore 2 through 0.6.3 and other products, has a STARTTLS buffering issue that affects IMAP, SMTP, and POP3. When a server sends a "begin TLS" response, the client reads additional data (e.g., from a meddler-in-the-middle attacker) and evaluates it in a TLS context, aka "response injection."

Record
ALPINE-CVE-2020-15953
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Updated
2026-11-03
OSV 7.4

LibEtPan through 1.9.4, as used in MailCore 2 through 0.6.3 and other products, has a STARTTLS buffering issue that affects IMAP, SMTP, and POP3. When a server sends a "begin TLS" response, the client reads additional data (e.g., from a meddler-in-the-middle attacker) and evaluates it in a TLS context, aka "response injection."

Record
CVE-2020-15953
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Updated
2026-11-02
Show 7 moreShow less
OSVDEBIAN-CVE-2020-15953 7.4

LibEtPan through 1.9.4, as used in MailCore 2 through 0.6.3 and other products, has a STARTTLS buffering issue that affects IMAP, SMTP, and POP3. When a server sends a "begin TLS" response, the client reads additional data (e.g., from a meddler-in-the-middle attacker) and evaluates it in a TLS context, aka "response injection."

Record
DEBIAN-CVE-2020-15953
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Updated
2026-11-02
OSVUBUNTU-CVE-2020-15953 7.4

LibEtPan through 1.9.4, as used in MailCore 2 through 0.6.3 and other products, has a STARTTLS buffering issue that affects IMAP, SMTP, and POP3. When a server sends a "begin TLS" response, the client reads additional data (e.g., from a meddler-in-the-middle attacker) and evaluates it in a TLS context, aka "response injection."

Record
UBUNTU-CVE-2020-15953
CVSS 3.1
7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Updated
2026-11-02
OSVMGASA-2020-0366 No score

Updated libetpan packages fix a security vulnerability

LibEtPan through 1.9.4, as used in MailCore 2 through 0.6.3 and other products, has a STARTTLS buffering issue that affects IMAP, SMTP, and POP3. When a server sends a "begin TLS" response, the client reads additional data (e.g., from a meddler-in-the-middle attacker) and evaluates it in a TLS context, aka "response injection". (CVE-2020-15953).

Record
MGASA-2020-0366
Updated
2026-11-02
OSVopenSUSE-SU-2020:1454-1 No score

Security update for libetpan

This update for libetpan fixes the following issues:

Update to 1.9.4 (boo#1174579, CVE-2020-15953):

  • Bugfixes on QUOTA
  • Varios warning fixes & build fixes

Update to version 1.9.3

  • Added IMAP CLIENTID / SMTP CLIENTID support
  • Use Cyrus SASL 2.1.27

Update to version 1.9.2

  • Support of TLS SNI
  • LMDB for cache DB
  • Fixed build with recent versions of curl
Record
openSUSE-SU-2020:1454-1
Updated
2026-11-02
OSVopenSUSE-SU-2020:1505-1 No score

Security update for libetpan

This update for libetpan fixes the following issues:

Update to 1.9.4 (boo#1174579, CVE-2020-15953):

  • Bugfixes on QUOTA
  • Varios warning fixes & build fixes

Update to version 1.9.3

  • Added IMAP CLIENTID / SMTP CLIENTID support
  • Use Cyrus SASL 2.1.27

Update to version 1.9.2

  • Support of TLS SNI
  • LMDB for cache DB
  • Fixed build with recent versions of curl

This update was imported from the openSUSE:Leap:15.2:Update update project.

Record
openSUSE-SU-2020:1505-1
Updated
2026-11-02
OSVopenSUSE-SU-2024:10938-1 No score

libetpan-devel-1.9.4-1.7 on GA media

These are all security issues fixed in the libetpan-devel-1.9.4-1.7 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2024:10938-1
Updated
2026-11-02
OSVUSN-4598-1 No score

libetpan vulnerability

It was discovered that LibEtPan incorrectly handled STARTTLS when using IMAP, SMTP and POP3. A remote attacker could possibly use this issue to perform a response injection attack. (CVE-2020-15953)

Record
USN-4598-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
libetpan
Alpine:v3.13
 before 1.9.4-r1
1.9.4-r1
libetpan
Alpine:v3.14
 before 1.9.4-r1
1.9.4-r1
libetpan
Alpine:v3.15
 before 1.9.4-r1
1.9.4-r1
libetpan
Alpine:v3.16
 before 1.9.4-r1
1.9.4-r1
libetpan
Alpine:v3.17
 before 1.9.4-r1
1.9.4-r1
libetpan
Alpine:v3.18
 before 1.9.4-r1
1.9.4-r1
libetpan
Alpine:v3.19
 before 1.9.4-r1
1.9.4-r1
libetpan
Alpine:v3.20
 before 1.9.4-r1
1.9.4-r1
libetpan
Alpine:v3.21
 before 1.9.4-r1
1.9.4-r1
libetpan
Alpine:v3.22
 before 1.9.4-r1
1.9.4-r1
Show 17 moreShow less
Affected packages
PackageAffectedFixed
libetpan
Alpine:v3.23
 before 1.9.4-r1
1.9.4-r1
libetpan
Alpine:v3.24
 before 1.9.4-r1
1.9.4-r1
libetpan
Debian:12
 before 1.9.4-3
1.9.4-3
libetpan
Debian:13
 before 1.9.4-3
1.9.4-3
libetpan
Debian:14
 before 1.9.4-3
1.9.4-3
libetpan
Debian:9
 before 1.6-3+deb9u1, plus listed versions
1.6-3
1.6-3+deb9u1
libetpan
Mageia:7
 before 1.9.3-1.1.mga7
1.9.3-1.1.mga7
libetpan
Ubuntu:16.04:LTS
 before 1.6-1ubuntu0.1, plus listed versions
1.5-21.6-11.6-1build1
1.6-1ubuntu0.1
libetpan
Ubuntu:Pro:18.04:LTS
 All versions, plus listed versions
1.8.0-11.8.0-1ubuntu0.1~esm1
 None known
libetpan
Ubuntu:Pro:20.04:LTS
 All versions, plus listed versions
1.9.3-21.9.4-21.9.4-2ubuntu0.1~esm1
 None known
libetpan
Ubuntu:22.04:LTS
 All versions, plus listed versions
1.9.4-31.9.4-3+deb11u1build0.22.04.1
 None known
libetpan
Ubuntu:24.04:LTS
 All versions, plus listed versions
1.9.4-3.11.9.4-3.21.9.4-3.2build11.9.4-3.2build2
 None known
libetpan
Ubuntu:25.10
 All versions, plus listed versions
1.9.4-51.9.4-6
 None known
libetpan
Ubuntu:26.10
 All versions, plus listed versions
1.9.4-81.10.0-11.10.0-1.1
 None known
libetpan
Ubuntu:26.04:LTS
 All versions, plus listed versions
1.9.4-61.9.4-71.9.4-8
 None known
libetpan
openSUSE:Leap 15.2
 before 1.9.4-lp152.3.3.1
1.9.4-lp152.3.3.1
libetpan
SUSE:Package Hub 15 SP2
 before 1.9.4-bp152.4.3.1
1.9.4-bp152.4.3.1

History

History
RecordedChangedSources
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-2020-15953 is a high vulnerability (CVSS 7.4) in Libetpan Project Libetpan, published July 27, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.40%, the 84th percentile. Fixed in libetpan 1.9.4-r1.

References

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