CVE-2020-11993

Exp

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.

Published: 2020-08-07 Last update: 2025-05-01 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-11993 is rated High Exploit Risk (73.8/100): CVSS High severity, with high exploitation likelihood (EPSS 27.45%, 97th percentile). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2020-11993

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2020-11993

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-31 33.36% 27.45% -5.91%
2 2026-03-04 18.21% 33.36% +15.15%
3 2026-03-01 — 18.21% —

Full EPSS history (46 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-11993

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2020-11993

OS Trackers for CVE-2020-11993

vendor priority summary link
alpine — CVE-2020-11993: 1 source package rows (apache2); 10 state rows across 10 repos (3.10-main, 3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 10, open 0. https://security.alpinelinux.org/vuln/CVE-2020-11993
debian not yet assigned CVE-2020-11993 not yet assigned priority: Debian including 1 source packages (apache2), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2020-11993
gentoo normal CVE-2020-11993: 1 GLSA(s) (202008-04), 1 atom(s) (www-servers/apache); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2020-11993
redhat medium — https://access.redhat.com/security/cve/CVE-2020-11993
suse medium CVE-2020-11993 severity moderate: SUSE including 296 source package names (amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, amazon/suse-sles-15-sp1-chost-byos-v20220127-hvm-ssd-x86_64, …), 498 product×package rows across 60 product lines (HPE Helion OpenStack 8, Image SLES15-SP3-EC2-HVM, … (60 product lines)): Fixed 264, Known Affected 231, Known Not Affected 3. https://www.suse.com/security/cve/CVE-2020-11993/
ubuntu medium CVE-2020-11993 medium priority: Ubuntu including 1 source packages (apache2), 5 status rows across 5 suites (bionic, focal, trusty, upstream, xenial): released 3, not-affected 2. https://ubuntu.com/security/CVE-2020-11993

Affected software / configurations for CVE-2020-11993

Vendor Product Version Raw CPE
apache http_server >= 2.4.20, < 2.4.44 cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:*
netapp clustered_data_ontap — cpe:2.3:a:netapp:clustered_data_ontap:-:*:*:*:*:*:*:*
canonical ubuntu_linux 16.04 cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 18.04 cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 20.04 cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:*
opensuse leap 15.1 cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*
opensuse leap 15.2 cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
fedoraproject fedora 31 cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*
fedoraproject fedora 32 cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
oracle communications_element_manager >= 8.2.0, <= 8.2.2 cpe:2.3:a:oracle:communications_element_manager:*:*:*:*:*:*:*:*
oracle communications_session_report_manager >= 8.2.0, <= 8.2.2 cpe:2.3:a:oracle:communications_session_report_manager:*:*:*:*:*:*:*:*
oracle communications_session_route_manager >= 8.2.0, <= 8.2.2 cpe:2.3:a:oracle:communications_session_route_manager:*:*:*:*:*:*:*:*
oracle enterprise_manager_ops_center 12.4.0.0 cpe:2.3:a:oracle:enterprise_manager_ops_center:12.4.0.0:*:*:*:*:*:*:*
oracle hyperion_infrastructure_technology 11.1.2.4 cpe:2.3:a:oracle:hyperion_infrastructure_technology:11.1.2.4:*:*:*:*:*:*:*
oracle instantis_enterprisetrack 17.1 cpe:2.3:a:oracle:instantis_enterprisetrack:17.1:*:*:*:*:*:*:*
oracle instantis_enterprisetrack 17.2 cpe:2.3:a:oracle:instantis_enterprisetrack:17.2:*:*:*:*:*:*:*
oracle instantis_enterprisetrack 17.3 cpe:2.3:a:oracle:instantis_enterprisetrack:17.3:*:*:*:*:*:*:*
oracle zfs_storage_appliance_kit 8.8 cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:*:*:*:*:*:*:*

References for CVE-2020-11993

URL Tags
http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00068.html Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00071.html Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00081.html Mailing List Third Party Advisory
http://packetstormsecurity.com/files/160393/Apache-2-HTTP2-Module-Concurrent-Pool-Usage.html Exploit Third Party Advisory VDB Entry
https://httpd.apache.org/security/vulnerabilities_24.html#CVE-2020-11993 Vendor Advisory
https://lists.apache.org/thread.html/r06f0d87ebb6d59ed8379633f36f72f5b1f79cadfda72ede0830b42cf%40%3Ccvs.httpd.apache.org%3E Patch
https://lists.apache.org/thread.html/r09bb998baee74a2c316446bd1a41ae7f8d7049d09d9ff991471e8775%40%3Ccvs.httpd.apache.org%3E Patch
https://lists.apache.org/thread.html/r2c6083f6a2027914a0f5b54e2a1f4fa98c03f8693b58460911818255%40%3Ccvs.httpd.apache.org%3E Patch
https://lists.apache.org/thread.html/r3c5c3104813c1c5508b55564b66546933079250a46ce50eee90b2e36%40%3Ccvs.httpd.apache.org%3E Patch
https://lists.apache.org/thread.html/r5debe8f82728a00a4a68bc904dd6c35423bdfc8d601cfb4579f38bf1%40%3Cdev.httpd.apache.org%3E Patch
https://lists.apache.org/thread.html/r623de9b2b2433a87f3f3a15900419fc9c00c77b26936dfea4060f672%40%3Cdev.httpd.apache.org%3E Patch
https://lists.apache.org/thread.html/r76142b8c5119df2178be7c2dba88fde552eedeec37ea993dfce68d1d%40%3Ccvs.httpd.apache.org%3E Patch
https://lists.apache.org/thread.html/r9e9f1a7609760f0f80562eaaec2aa3c32d525c3e0fca98b475240c71%40%3Cdev.httpd.apache.org%3E Patch
https://lists.apache.org/thread.html/r9f93cf6dde308d42a9c807784e8102600d0397f5f834890708bf6920%40%3Ccvs.httpd.apache.org%3E Patch
https://lists.apache.org/thread.html/rc998b18880df98bafaade071346690c2bc1444adaa1a1ea464b93f0a%40%3Ccvs.httpd.apache.org%3E Patch
https://lists.apache.org/thread.html/rdf3e5d0a5f5c3d90d6013bccc6c4d5af59cf1f8c8dea5d9a283d13ce%40%3Ccvs.httpd.apache.org%3E Patch
https://lists.apache.org/thread.html/rf6449464fd8b7437704c55f88361b66f12d5b5f90bcce66af4be4ba9%40%3Ccvs.httpd.apache.org%3E Patch
https://lists.apache.org/thread.html/rf71eb428714374a6f9ad68952e23611ec7807b029fd6a1b4f5f732d9%40%3Ccvs.httpd.apache.org%3E Patch
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4NKWG2EXAQQB6LMLATKZ7KLSRGCSHVAN/ Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ITVFDBVM6E3JF3O7RYLRPRCH3RDRHJJY/ Third Party Advisory
https://security.gentoo.org/glsa/202008-04 Third Party Advisory
https://security.netapp.com/advisory/ntap-20200814-0005/ Third Party Advisory
https://usn.ubuntu.com/4458-1/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4757 Third Party Advisory
https://www.oracle.com/security-alerts/cpujan2021.html Third Party Advisory
https://www.oracle.com/security-alerts/cpuoct2020.html Vendor Advisory
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