CVE-2018-16844

nginx before versions 1.15.6 and 1.14.1 has a vulnerability in the implementation of HTTP/2 that can allow for excessive CPU usage. This issue affects nginx compiled with the ngx_http_v2_module (not compiled by default) if the 'http2' option of the 'listen' directive is used in a configuration file.

Published: 2018-11-07 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2018-16844 is rated High Risk (65/100): CVSS High severity, with high exploitation likelihood (EPSS 12.40%, 96th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. EPSS rose +1.52% over the last day, indicating growing attacker interest. 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-2018-16844

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 10.88% 12.40% +1.52%
2 2026-06-04 11.14% 10.88% -0.26%
3 2026-05-22 — 11.14% —

Full EPSS history (53 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2018-16844

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]
5.3 3.0 MEDIUM
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L 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:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 3.9 1.4 [email protected]
7.8 2.0 HIGH
AV:N/AC:L/Au:N/C:N/I:N/A:C 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:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:C)
Complete availability impact.
 10.0 6.9 [email protected]

Weakness enumeration for CVE-2018-16844

OS Trackers for CVE-2018-16844

vendor priority summary link
alpine high CVE-2018-16844: 1 source package rows (nginx); 15 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 5. https://security.alpinelinux.org/vuln/CVE-2018-16844
debian not yet assigned CVE-2018-16844 not yet assigned priority: Debian including 1 source packages (nginx), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2018-16844
redhat medium — https://access.redhat.com/security/cve/CVE-2018-16844
suse medium CVE-2018-16844 severity moderate: SUSE including 21 source package names (nginx-1.0, nginx-1.14.2-16.1, …), 22 product×package rows across 12 product lines (SUSE Lifecycle Management Server 1.3, SUSE Linux Enterprise Module for Server Applications 15, … (12 product lines)): Fixed 20, Known Not Affected 2. https://www.suse.com/security/cve/CVE-2018-16844/
ubuntu medium CVE-2018-16844 medium priority: Ubuntu including 1 source packages (nginx), 5 status rows across 5 suites (bionic, cosmic, trusty, upstream, xenial): released 4, not-affected 1. https://ubuntu.com/security/CVE-2018-16844

Affected software / configurations for CVE-2018-16844

Vendor Product Version Raw CPE
f5 nginx >= 1.9.5, < 1.14.1 cpe:2.3:a:f5:nginx:*:*:*:*:*:*:*:*
f5 nginx >= 1.15.0, < 1.15.6 cpe:2.3:a:f5:nginx:*:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
canonical ubuntu_linux 14.04 cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
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 18.10 cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:*
apple xcode < 13.0 cpe:2.3:a:apple:xcode:*:*:*:*:*:*:*:*

References for CVE-2018-16844

URL Tags
http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00035.html Third Party Advisory
http://mailman.nginx.org/pipermail/nginx-announce/2018/000220.html Mailing List Vendor Advisory
http://seclists.org/fulldisclosure/2021/Sep/36 Mailing List Third Party Advisory
http://www.securityfocus.com/bid/105868 Third Party Advisory VDB Entry
http://www.securitytracker.com/id/1042038 Third Party Advisory VDB Entry
https://access.redhat.com/errata/RHSA-2018:3680 Third Party Advisory
https://access.redhat.com/errata/RHSA-2018:3681 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-16844 Issue Tracking
https://support.apple.com/kb/HT212818 Third Party Advisory
https://usn.ubuntu.com/3812-1/ Third Party Advisory
https://www.debian.org/security/2018/dsa-4335 Third Party Advisory
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