CVE-2011-3639

CVE-2011-3639 is a medium-severity vulnerability in Apache Http Server with a CVSS 2.0 base score of 4.3. Its EPSS exploit-prediction score of 53% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-20.

Key facts

Description

The mod_proxy module in the Apache HTTP Server 2.0.x through 2.0.64 and 2.2.x before 2.2.18, when the Revision 1179239 patch is in place, does not properly interact with use of (1) RewriteRule and (2) ProxyPassMatch pattern matches for configuration of a reverse proxy, which allows remote attackers to send requests to intranet servers by using the HTTP/0.9 protocol with a malformed URI containing an initial @ (at sign) character. NOTE: this vulnerability exists because of an incomplete fix for CVE-2011-3368.

Frequently asked questions

What is CVE-2011-3639?
The mod_proxy module in the Apache HTTP Server 2.0.x through 2.0.64 and 2.2.x before 2.2.18, when the Revision 1179239 patch is in place, does not properly interact with use of (1) RewriteRule and (2) ProxyPassMatch pattern matches for configuration of a reverse proxy, which allows remote attackers to send requests to intranet servers by using the HTTP/0.9 protocol with a malformed URI containing an initial @ (at sign) character. NOTE: this vulnerability exists because of an incomplete fix for CVE-2011-3368.
How severe is CVE-2011-3639?
CVE-2011-3639 has a CVSS 2.0 base score of 4.3, rated medium severity.
Is CVE-2011-3639 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 53% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2011-3639?
CVE-2011-3639 primarily affects Apache Http Server. In total, 76 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2011-3639?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2011-3639 published?
CVE-2011-3639 was published on 2011-11-30 and last updated on 2026-06-16.

References

Affected products (76)

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Threat intelligence

Threat-intel indicators referencing this CVE: