Search for vulnerabilities
Vulnerability details: VCID-pv8t-qmzf-q3hh
Vulnerability ID VCID-pv8t-qmzf-q3hh
Aliases CVE-2021-33193
Summary A crafted method sent through HTTP/2 will bypass validation and be forwarded by mod_proxy, which can lead to request splitting or cache poisoning. This issue affects Apache HTTP Server 2.4.17 to 2.4.48.
Status Published
Exploitability 0.5
Weighted Severity 8.0
Risk 4.0
Affected and Fixed Packages Package Details
Weaknesses (1)
CWE-476 NULL Pointer Dereference
System Score Found at
cvssv3 7.5 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-33193.json
epss 0.01014 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01116 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01116 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01116 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01116 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01229 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01229 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01229 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01229 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01229 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01229 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01229 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01229 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01298 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01298 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01298 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01298 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01298 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01298 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01352 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01352 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.01352 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.0175 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.0175 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
epss 0.0175 https://api.first.org/data/v1/epss?cve=CVE-2021-33193
cvssv3.1 9.1 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
apache_httpd moderate https://httpd.apache.org/security/json/CVE-2021-33193.json
cvssv2 5.0 https://nvd.nist.gov/vuln/detail/CVE-2021-33193
cvssv3.1 7.5 https://nvd.nist.gov/vuln/detail/CVE-2021-33193
archlinux High https://security.archlinux.org/AVG-2289
Reference id Reference type URL
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-33193.json
https://api.first.org/data/v1/epss?cve=CVE-2021-33193
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-33193
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
https://github.com/apache/httpd/commit/ecebcc035ccd8d0e2984fe41420d9e944f456b3c.patch
https://lists.apache.org/thread.html/re4162adc051c1a0a79e7a24093f3776373e8733abaff57253fef341d%40%3Ccvs.httpd.apache.org%3E
https://lists.apache.org/thread.html/ree7519d71415ecdd170ff1889cab552d71758d2ba2904a17ded21a70%40%3Ccvs.httpd.apache.org%3E
https://lists.debian.org/debian-lts-announce/2023/03/msg00002.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DSM6UWQICBJ2TU727RENU3HBKEAFLT6T/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EUVJVRJRBW5QVX4OY3NOHZDQ3B3YOTSG/
https://portswigger.net/research/http2
https://security.netapp.com/advisory/ntap-20210917-0004/
https://www.oracle.com/security-alerts/cpuapr2022.html
https://www.oracle.com/security-alerts/cpujan2022.html
1966728 https://bugzilla.redhat.com/show_bug.cgi?id=1966728
AVG-2289 https://security.archlinux.org/AVG-2289
cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:*
cpe:2.3:a:oracle:secure_backup:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:oracle:secure_backup:*:*:*:*:*:*:*:*
cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:*:*:*:*:*:*:*
cpe:2.3:a:tenable:tenable.sc:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:tenable:tenable.sc:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
CVE-2021-33193 https://httpd.apache.org/security/json/CVE-2021-33193.json
CVE-2021-33193 https://nvd.nist.gov/vuln/detail/CVE-2021-33193
RHSA-2022:1915 https://access.redhat.com/errata/RHSA-2022:1915
RHSA-2022:6753 https://access.redhat.com/errata/RHSA-2022:6753
RHSA-2022:7143 https://access.redhat.com/errata/RHSA-2022:7143
RHSA-2022:7144 https://access.redhat.com/errata/RHSA-2022:7144
USN-5090-1 https://usn.ubuntu.com/5090-1/
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Found at https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-33193.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N Found at https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: AV:N/AC:L/Au:N/C:N/I:P/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-33193
Exploitability (E) Access Vector (AV) Access Complexity (AC) Authentication (Au) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

high

functional

unproven

proof_of_concept

not_defined

local

adjacent_network

network

high

medium

low

multiple

single

none

none

partial

complete

none

partial

complete

none

partial

complete
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-33193
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.7619
EPSS Score 0.01014
Published At Aug. 17, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:29:08.812055+00:00 Apache HTTPD Importer Import https://httpd.apache.org/security/json/CVE-2021-33193.json 37.0.0