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CVE-2020-35680

smtpd/lka_filter.c in OpenSMTPD before 6.8.0p1, in certain configurations, allows remote...

7.5 HighFix available

CVE-2020-35680 is a high vulnerability (CVSS 7.5) in Opensmtpd, published December 24, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 3.65%, the 89th percentile. Fixed in opensmtpd 6.6.4p1-r1.

smtpd/lka_filter.c in OpenSMTPD before 6.8.0p1, in certain configurations, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted pattern of client activity, because the filter state machine does not properly maintain the I/O channel between the SMTP engine and the filters layer.

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
None
Availability
High

Exploit likelihood

3.65%Up 1.7 points since Apr 14, 2021
90%50%10%1%

What each source reports

NVD Score used 7.5

smtpd/lka_filter.c in OpenSMTPD before 6.8.0p1, in certain configurations, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted pattern of client activity, because the filter state machine does not properly maintain the I/O channel between the SMTP engine and the filters layer.

Record
CVE-2020-35680
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0
5.0 MediumAV:N/AC:L/Au:N/C:N/I:N/A:P
Weakness
CWE-476
Updated
2026-11-02
CVE List No score

smtpd/lka_filter.c in OpenSMTPD before 6.8.0p1, in certain configurations, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted pattern of client activity, because the filter state machine does not properly maintain the I/O channel between the SMTP engine and the filters layer.

Record
CVE-2020-35680
Updated
2026-11-02
EUVDEUVD-2020-23340 No score

smtpd/lka_filter.c in OpenSMTPD before 6.8.0p1, in certain configurations, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted pattern of client activity, because the filter state machine does not properly maintain the I/O channel between the SMTP engine and the filters layer.

Record
EUVD-2020-23340
Updated
2026-11-03
GitHub AdvisoriesGHSA-924w-4qc7-pc84 7.5

smtpd/lka_filter.c in OpenSMTPD before 6.8.0p1, in certain configurations, allows remote...

smtpd/lka_filter.c in OpenSMTPD before 6.8.0p1, in certain configurations, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted pattern of client activity, because the filter state machine does not properly maintain the I/O channel between the SMTP engine and the filters layer.

Record
GHSA-924w-4qc7-pc84
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-476
Updated
2026-11-02
OSVALPINE-CVE-2020-35680 7.5

smtpd/lka_filter.c in OpenSMTPD before 6.8.0p1, in certain configurations, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted pattern of client activity, because the filter state machine does not properly maintain the I/O channel between the SMTP engine and the filters layer.

Record
ALPINE-CVE-2020-35680
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSV 7.5

smtpd/lka_filter.c in OpenSMTPD before 6.8.0p1, in certain configurations, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted pattern of client activity, because the filter state machine does not properly maintain the I/O channel between the SMTP engine and the filters layer.

Record
CVE-2020-35680
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVDEBIAN-CVE-2020-35680 7.5

smtpd/lka_filter.c in OpenSMTPD before 6.8.0p1, in certain configurations, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted pattern of client activity, because the filter state machine does not properly maintain the I/O channel between the SMTP engine and the filters layer.

Record
DEBIAN-CVE-2020-35680
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2020-35680 7.5

smtpd/lka_filter.c in OpenSMTPD before 6.8.0p1, in certain configurations, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted pattern of client activity, because the filter state machine does not properly maintain the I/O channel between the SMTP engine and the filters layer.

Record
UBUNTU-CVE-2020-35680
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
opensmtpd
Alpine:v3.11
 before 6.6.4p1-r1
6.6.4p1-r1
opensmtpd
Alpine:v3.12
 before 6.6.4p1-r2
6.6.4p1-r2
opensmtpd
Alpine:v3.13
 before 6.7.1p1-r1
6.7.1p1-r1
opensmtpd
Debian:12
 before 6.8.0p2-1
6.8.0p2-1
opensmtpd
Debian:13
 before 6.8.0p2-1
6.8.0p2-1
opensmtpd
Debian:14
 before 6.8.0p2-1
6.8.0p2-1
opensmtpd
Ubuntu:Pro:14.04:LTS
 All versions, plus listed versions
5.3.3p1-45.4.1p1-15.4.1p1-1ubuntu0.1~esm1
 None known
opensmtpd
Ubuntu:20.04:LTS
 All versions, plus listed versions
6.0.3p1-66.0.3p1-6build16.6.1p1-16.6.1p1-36.6.1p1-46.6.1p1-56.6.2p1-16.6.4p1-1
 None known
opensmtpd
Ubuntu:22.04:LTS
 All versions, plus listed versions
6.8.0p2-36.8.0p2-46.8.0p2-4build1
 None known
opensmtpd
Ubuntu:24.04:LTS
 All versions, plus listed versions
7.3.0p1-17.3.0p2-17.4.0p1-17.4.0p1-1build27.4.0p1-1build4
 None known
opensmtpd
Ubuntu:25.10
 All versions, plus listed versions
7.5.0p0-17.7.0p0-1
 None known
opensmtpd
Ubuntu:26.10
 All versions, plus listed versions
7.8.0p0-27.8.0p0-2build1
 None known
opensmtpd
Ubuntu:26.04:LTS
 All versions, plus listed versions
7.7.0p0-17.8.0p0-17.8.0p0-2
 None known

History

History
WhenChangedSources
2026-11-03aliasesEUVD
2026-11-02createdCVE List, GitHub Advisories, NVD, OSV

References

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