CVE-2009-3555

CVE-2009-3555 is a critical-severity vulnerability in Apache Http Server with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 87% places it in the 100th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-295.

Key facts

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.

Frequently asked questions

What is CVE-2009-3555?
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.
How severe is CVE-2009-3555?
CVE-2009-3555 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2009-3555 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 87% (100th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2009-3555?
CVE-2009-3555 primarily affects Apache Http Server. In total, 21 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2009-3555?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2009-3555 published?
CVE-2009-3555 was published on 2009-11-09 and last updated on 2026-06-16.

References

Affected products (21)

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Threat intelligence

Threat-intel indicators referencing this CVE: