CVE-2018-1333 | DoS for HTTP/2 connections by crafted requests

By specially crafting HTTP/2 requests, workers would be allocated 60 seconds longer than necessary, leading to worker exhaustion and a denial of service. Fixed in Apache HTTP Server 2.4.34 (Affected 2.4.18-2.4.30,2.4.33).

Published: 2018-06-18 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2018-1333 is rated Moderate Risk (60.1/100): CVSS High severity, with high exploitation likelihood (EPSS 17.10%, 97th 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-2018-1333

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 20.81% 17.10% -3.71%
2 2026-05-26 22.31% 20.81% -1.50%
3 2026-04-27 — 22.31% —

Full EPSS history (57 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2018-1333

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.0 HIGH
CVSS:3.0/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]
5.0 2.0 MEDIUM
AV:N/AC:L/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: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:P)
Partial availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2018-1333

OS Trackers for CVE-2018-1333

vendor priority summary link
alpine high CVE-2018-1333: 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-2018-1333
debian not yet assigned CVE-2018-1333 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-2018-1333
redhat medium — https://access.redhat.com/security/cve/CVE-2018-1333
suse low CVE-2018-1333 severity low: SUSE including 43 source package names (apache2, apache2-2.4.23-29.21.1, …), 85 product×package rows across 20 product lines (SUSE Linux Enterprise High Performance Computing 12 SP5, SUSE Linux Enterprise Module for Open Buildservice Development Tools 15 SP1, … (20 product lines)): Fixed 67, Known Not Affected 18. https://www.suse.com/security/cve/CVE-2018-1333/
ubuntu low CVE-2018-1333 low priority: Ubuntu including 1 source packages (apache2), 4 status rows across 4 suites (bionic, trusty, upstream, xenial): not-affected 2, released 2. https://ubuntu.com/security/CVE-2018-1333

Affected software / configurations for CVE-2018-1333

Vendor Product Version Raw CPE
apache http_server >= 2.4.18, <= 2.4.30 cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:*
apache http_server 2.4.33 cpe:2.3:a:apache:http_server:2.4.33:*:*:*:*:*:*:*
redhat jboss_core_services 1.0 cpe:2.3:a:redhat:jboss_core_services:1.0:*:*:*:*:*:*:*
canonical ubuntu_linux 18.04 cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
netapp cloud_backup — cpe:2.3:a:netapp:cloud_backup:-:*:*:*:*:*:*:*
netapp storage_automation_store — cpe:2.3:a:netapp:storage_automation_store:-:*:*:*:*:*:*:*

References for CVE-2018-1333

URL Tags
http://www.securitytracker.com/id/1041402 Third Party Advisory VDB Entry
https://access.redhat.com/errata/RHSA-2018:3558 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:0366 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:0367 Third Party Advisory
https://httpd.apache.org/security/vulnerabilities_24.html#CVE-2018-1333 Vendor Advisory
https://lists.apache.org/thread.html/56c2e7cc9deb1c12a843d0dc251ea7fd3e7e80293cde02fcd65286ba%40%3Ccvs.httpd.apache.org%3E
https://lists.apache.org/thread.html/84a3714f0878781f6ed84473d1a503d2cc382277e100450209231830%40%3Ccvs.httpd.apache.org%3E
https://lists.apache.org/thread.html/r06f0d87ebb6d59ed8379633f36f72f5b1f79cadfda72ede0830b42cf%40%3Ccvs.httpd.apache.org%3E
https://lists.apache.org/thread.html/r15f9aa4427581a1aecb4063f1b4b983511ae1c9935e2a0a6876dad3c%40%3Ccvs.httpd.apache.org%3E
https://lists.apache.org/thread.html/r76142b8c5119df2178be7c2dba88fde552eedeec37ea993dfce68d1d%40%3Ccvs.httpd.apache.org%3E
https://lists.apache.org/thread.html/r9f93cf6dde308d42a9c807784e8102600d0397f5f834890708bf6920%40%3Ccvs.httpd.apache.org%3E
https://lists.apache.org/thread.html/rc998b18880df98bafaade071346690c2bc1444adaa1a1ea464b93f0a%40%3Ccvs.httpd.apache.org%3E
https://lists.apache.org/thread.html/rd18c3c43602e66f9cdcf09f1de233804975b9572b0456cc582390b6f%40%3Ccvs.httpd.apache.org%3E
https://lists.apache.org/thread.html/rd2fb621142e7fa187cfe12d7137bf66e7234abcbbcd800074c84a538%40%3Ccvs.httpd.apache.org%3E
https://lists.apache.org/thread.html/re3d27b6250aa8548b8845d314bb8a350b3df326cacbbfdfe4d455234%40%3Ccvs.httpd.apache.org%3E
https://lists.apache.org/thread.html/re473305a65b4db888e3556e4dae10c2a04ee89dcff2e26ecdbd860a9%40%3Ccvs.httpd.apache.org%3E
https://lists.apache.org/thread.html/rf6449464fd8b7437704c55f88361b66f12d5b5f90bcce66af4be4ba9%40%3Ccvs.httpd.apache.org%3E
https://security.netapp.com/advisory/ntap-20180926-0007/ Third Party Advisory
https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbux03909en_us Third Party Advisory
https://usn.ubuntu.com/3783-1/ Third Party Advisory
https://www.tenable.com/security/tns-2019-09
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