What’s Vulnerable › Vulnerabilities
CVE-2020-35680
- Severity: high (CVSS 7.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 3.7% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2020-12-24 · updated 2026-06-17
- Weakness: CWE-476
Description
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.
Affected products
- Fedoraproject Fedora: 32, 33
- Opensmtpd: before 6.8.0; 6.8.0, 6.8.0-patch1-rc1 — fixed in 6.8.0
How to fix
Upgrade to a fixed version: Opensmtpd 6.8.0. Check the vendor advisory for mitigations.
References
- https://github.com/openbsd/src/commit/6c3220444ed06b5796dedfd53a0f4becd903c0d1
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5LKTFBQCHGMVPR4IZWHQIYAPM5J3LN3J/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TYAYXRV2DM5K4RU7RHCDZSA2UF6VCTRC/
- https://poolp.org/posts/2020-12-24/december-2020-opensmtpd-6.8.0p1-released-fixed-several-bugs-proposed-several-diffs-book-is-on-github/
- https://security.gentoo.org/glsa/202105-12
- https://www.mail-archive.com/misc%40opensmtpd.org/msg05188.html
- https://github.com/openbsd/src/commit/6c3220444ed06b5796dedfd53a0f4becd903c0d1
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5LKTFBQCHGMVPR4IZWHQIYAPM5J3LN3J/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TYAYXRV2DM5K4RU7RHCDZSA2UF6VCTRC/
- https://poolp.org/posts/2020-12-24/december-2020-opensmtpd-6.8.0p1-released-fixed-several-bugs-proposed-several-diffs-book-is-on-github/
- https://security.gentoo.org/glsa/202105-12
- https://www.mail-archive.com/misc%40opensmtpd.org/msg05188.html
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