CVE-2020-11100

In hpack_dht_insert in hpack-tbl.c in the HPACK decoder in HAProxy 1.8 through 2.x before 2.1.4, a remote attacker can write arbitrary bytes around a certain location on the heap via a crafted HTTP/2 request, possibly causing remote code execution.

Published: 2020-04-02 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-11100 is rated Moderate Risk (64.9/100): CVSS High severity, with high exploitation likelihood (EPSS 60.73%, 99th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. High exploitation likelihood—assess exposure and prioritize remediation.

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

Exploit prediction scoring system (EPSS) score for CVE-2020-11100

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 2026-06-15 74.40% 60.73% -13.67%
2 2026-05-30 74.79% 74.40% -0.40%
3 2026-05-27 — 74.79% —

Full EPSS history (48 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-11100

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:L)
A normal user session is enough; they don’t have to be admin.
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:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]
6.5 2.0 MEDIUM
AV:N/AC:L/Au:S/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.0 6.4 [email protected]

Weakness enumeration for CVE-2020-11100

OS Trackers for CVE-2020-11100

vendor priority summary link
alpine high CVE-2020-11100: 1 source package rows (haproxy); 17 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 17, open 0. https://security.alpinelinux.org/vuln/CVE-2020-11100
debian not yet assigned CVE-2020-11100 not yet assigned priority: Debian including 1 source packages (haproxy), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2020-11100
gentoo normal CVE-2020-11100: 1 GLSA(s) (202012-22), 1 atom(s) (net-proxy/haproxy); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2020-11100
redhat critical — https://access.redhat.com/security/cve/CVE-2020-11100
suse high CVE-2020-11100 severity important: SUSE including 11 source package names (haproxy, haproxy-1.8.15-6.el8_1.1, …), 28 product×package rows across 28 product lines (HPE Helion OpenStack 8, HPE Helion OpenStack Cloud 8, … (28 product lines)): Known Not Affected 17, Fixed 11. https://www.suse.com/security/cve/CVE-2020-11100/
ubuntu medium CVE-2020-11100 medium priority: Ubuntu including 1 source packages (haproxy), 5 status rows across 5 suites (bionic, eoan, trusty, upstream, xenial): released 3, DNE 1, not-affected 1. https://ubuntu.com/security/CVE-2020-11100

Affected software / configurations for CVE-2020-11100

Vendor Product Version Raw CPE
haproxy haproxy >= 1.8.0, < 2.1.4 cpe:2.3:a:haproxy:haproxy:*:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
redhat openshift_container_platform 3.11 cpe:2.3:a:redhat:openshift_container_platform:3.11:*:*:*:*:*:*:*
redhat openshift_container_platform 4.0 cpe:2.3:a:redhat:openshift_container_platform:4.0:*:*:*:*:*:*:*
fedoraproject fedora 30 cpe:2.3:o:fedoraproject:fedora:30:*:*:*:*:*:*:*
fedoraproject fedora 31 cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*
canonical ubuntu_linux 18.04 cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 19.10 cpe:2.3:o:canonical:ubuntu_linux:19.10:*:*:*:*:*:*:*
opensuse leap 15.1 cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*

References for CVE-2020-11100

URL Tags
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00002.html Mailing List Third Party Advisory
http://packetstormsecurity.com/files/157323/haproxy-hpack-tbl.c-Out-Of-Bounds-Write.html Third Party Advisory VDB Entry
http://www.haproxy.org Vendor Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1819111 Issue Tracking Third Party Advisory
https://bugzilla.suse.com/show_bug.cgi?id=1168023 Issue Tracking Third Party Advisory
https://git.haproxy.org/?p=haproxy.git%3Ba=commit%3Bh=5dfc5d5cd0d2128d77253ead3acf03a421ab5b88
https://lists.debian.org/debian-security-announce/2020/msg00052.html Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/264C7UL3X7L7QE74ZJ557IOUFS3J4QQC/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MNW5RZLIX7LOXRLV7WMHX22CI43XSXKW/
https://security.gentoo.org/glsa/202012-22 Third Party Advisory
https://usn.ubuntu.com/4321-1/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4649 Third Party Advisory
https://www.haproxy.org/download/2.1/src/CHANGELOG Release Notes Vendor Advisory
https://www.mail-archive.com/haproxy%40formilux.org/msg36876.html
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