CVE-2009-3555: The TLS protocol, and the SSL protocol 3.0 and possibly earlier, as used in Microsoft Internet Information Services (…

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 18 Nov 2009. It cites 1 public report, the first from 18 Nov 2009.

• packetstormsecurity.com

How likely is exploitation in the next 30 days?

87.3%

EPSS score, percentile 99.8 of all scored records. A probability estimated by FIRST, not a report of exploitation.

CISA's SSVC assessment in the CVE record lists exploitation as poc.

How severe?

9.8 Critical

CVSS v3.1 base score, from CISA's enrichment of the record

What should I do?

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

Advisories and patches (12)

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

The TLS protocol, and the SSL protocol 3.0 and possibly earlier, as used in Microsoft Internet Information Services (IIS) 7.0, mod_ssl in the Apache HTTP Server 2.2.14 and earlier, OpenSSL before 0.9.8l, GnuTLS 2.8.5 and earlier, Mozilla Network Security Services (NSS) 3.12.4 and earlier, multiple Cisco products, and other products, does not properly associate renegotiation handshakes with an existing connection, which allows man-in-the-middle attackers to insert data into HTTPS sessions, and possibly other types of sessions protected by TLS or SSL, by sending an unauthenticated request that is processed retroactively by a server in a post-renegotiation context, related to a "plaintext injection" attack, aka the "Project Mogul" issue.

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

What to do

Advisories and patches

• APPLE-SA-2010-05-18-1 (Vendor advisory)
• RHSA-2010:0167 (Vendor advisory)
• FEDORA-2009-12750 (Vendor advisory)
• RHSA-2010:0865 (Vendor advisory)
• GLSA-201406-32 (Vendor advisory)
• HPSBMU02799 (Vendor advisory)
• SSRT090249 (Vendor advisory)
• SUSE-SA:2010:061 (Vendor advisory)
• [4.5] 010: SECURITY FIX: November 26, 2009 (Vendor advisory)
• USN-927-5 (Vendor advisory)
• PM12247 (Vendor advisory)
• SUSE-SU-2011:0847 (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