CVE-2006-4434: Use-after-free vulnerability in Sendmail before 8.13.8 allows remote attackers to cause a denial of service (crash) v…

Is it exploited?

Reported, not confirmed by CISA. VulnCheck KEV lists it as exploited in the wild. CISA has not added it to its Known Exploited Vulnerabilities catalog as of 29 Oct 2026.

VulnCheck KEV lists it since 29 Aug 2006. It cites 1 public report, the first from 29 Aug 2006.

• isc.sans.edu

How likely is exploitation in the next 30 days?

4.5%

EPSS score, percentile 91.6 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

Not scored

The CVE record carries no CVSS score.

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

Advisories and patches (6)

Which versions are affected?

Not stated. The CVE record gives vendor and product as “n/a” and the version as “unspecified”.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; VulnCheck KEV, as of 30 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 30 Oct 2026. About the data.

Description

Use-after-free vulnerability in Sendmail before 8.13.8 allows remote attackers to cause a denial of service (crash) via a long "header line", which causes a previously freed variable to be referenced. NOTE: the original developer has disputed the severity of this issue, saying "The only denial of service that is possible here is to fill up the disk with core dumps if the OS actually generates different core dumps (which is unlikely)... the bug is in the shutdown code (finis()) which leads directly to exit(3), i.e., the process would terminate anyway, no mail delivery or receiption is affected."

Source: CVE List, as of 30 Oct 2026. About the data.

What to do

Advisories and patches

• [3.9] 20060825 005: SECURITY FIX: August 25, 2006 (Vendor advisory)
• DSA-1164 (Vendor advisory)
• MDKSA-2006:156 (Vendor advisory)
• SUSE-SR:2006:021 (Vendor advisory)
• 102664 (Vendor advisory)
• [3.8] 20060825 010: SECURITY FIX: August 25, 2006 (Vendor advisory)

This summary is based on the CVE record as of 30 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

The CVE record does not name affected products or versions: vendor and product are “n/a” and the version is “unspecified”.

Source: CVE List, as of 30 Oct 2026. About the data.

Timeline