What’s Vulnerable › Vulnerabilities

CVE-2020-11993

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 56.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2020-08-07 · updated 2026-06-17
• Weakness: CWE-444

Description

Apache HTTP Server versions 2.4.20 to 2.4.43 When trace/debug was enabled for the HTTP/2 module and on certain traffic edge patterns, logging statements were made on the wrong connection, causing concurrent use of memory pools. Configuring the LogLevel of mod_http2 above "info" will mitigate this vulnerability for unpatched servers.

Affected products

• Apache HTTP Server: from 2.4.20 before 2.4.44 — fixed in 2.4.44
• Canonical Ubuntu Linux: 16.04, 18.04, 20.04
• Debian Linux: 10.0
• Fedoraproject Fedora: 31, 32
• Clustered Data ONTAP: all versions
• openSUSE Leap: 15.1, 15.2
• Oracle Communications Element Manager: from 8.2.0 through 8.2.2
• Oracle Communications Session Report Manager: from 8.2.0 through 8.2.2
• Oracle Communications Session Route Manager: from 8.2.0 through 8.2.2
• Oracle Corporation Enterprise Manager Ops Center: 12.4.0.0
• Oracle Corporation Oracle Hyperion Infrastructure Technology: 11.1.2.4
• Oracle Instantis Enterprisetrack: 17.1, 17.2, 17.3
• Oracle Corporation Oracle ZFS Storage Appliance Kit: 8.8

How to fix

Upgrade to a fixed version: Apache HTTP Server 2.4.44. Check the vendor advisory for mitigations.

References

• http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00068.html
• http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00071.html
• http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00081.html
• http://packetstormsecurity.com/files/160393/Apache-2-HTTP2-Module-Concurrent-Pool-Usage.html
• https://httpd.apache.org/security/vulnerabilities_24.html#CVE-2020-11993
• https://lists.apache.org/thread.html/r06f0d87ebb6d59ed8379633f36f72f5b1f79cadfda72ede0830b42cf%40%3Ccvs.httpd.apache.org%3E
• https://lists.apache.org/thread.html/r09bb998baee74a2c316446bd1a41ae7f8d7049d09d9ff991471e8775%40%3Ccvs.httpd.apache.org%3E
• https://lists.apache.org/thread.html/r2c6083f6a2027914a0f5b54e2a1f4fa98c03f8693b58460911818255%40%3Ccvs.httpd.apache.org%3E
• https://lists.apache.org/thread.html/r3c5c3104813c1c5508b55564b66546933079250a46ce50eee90b2e36%40%3Ccvs.httpd.apache.org%3E
• https://lists.apache.org/thread.html/r5debe8f82728a00a4a68bc904dd6c35423bdfc8d601cfb4579f38bf1%40%3Cdev.httpd.apache.org%3E
• https://lists.apache.org/thread.html/r623de9b2b2433a87f3f3a15900419fc9c00c77b26936dfea4060f672%40%3Cdev.httpd.apache.org%3E
• https://lists.apache.org/thread.html/r76142b8c5119df2178be7c2dba88fde552eedeec37ea993dfce68d1d%40%3Ccvs.httpd.apache.org%3E

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