Vulnerability Report

CVE-2021-33193

Title: Request splitting or cache poisoning in Apache HTTP Server

Request Splitting/Cache Poisoning

Proof Of Concept

No public PoC currently indexed for CVE-2021-33193.

CWE Category NVD-CWE-noinfo
Published Date Aug 16, 2021
Modified Date May 01, 2025
Exploit Status Not Found
Score 7.5 CVSS v3.1
Exploit Probability (EPSS)
0.61%

Vulnerability Summary

CVE-2021-33193: 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.

Impacted Vendors

A
apache 1
N
novell 1
A
a1webserver 1
O
oracle 2
T
tenable 1

Reference Links

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.gentoo.org/glsa/202208-20 https://security.netapp.com/advisory/ntap-20210917-0004/ https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ https://www.oracle.com/security-alerts/cpuapr2022.html https://www.oracle.com/security-alerts/cpujan2022.html https://www.tenable.com/security/tns-2021-17 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.gentoo.org/glsa/202208-20 https://security.netapp.com/advisory/ntap-20210917-0004/ https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ https://www.oracle.com/security-alerts/cpuapr2022.html https://www.oracle.com/security-alerts/cpujan2022.html https://www.tenable.com/security/tns-2021-17
CVSS v3.1
Source Entity [email protected]
Severity HIGH
7.5
Attack Vector
NETWORK
Complexity
LOW
Privileges
N/A
Interaction
NONE
Confidentiality
N/A
Integrity
N/A
Availability
N/A
Scope
UNCHANGED
RAW VECTOR CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS v2.0
Source Entity [email protected]
Severity MEDIUM
5.0
Access Vector
N/A
Authentication
N/A
RAW VECTOR AV:N/AC:L/Au:N/C:N/I:P/A:N

Associated Attack Patterns (CAPEC)

Total: Patterns

CVE-2021-33193 Exploits & PoCs (Proof Of Concept)

No public PoCs found in our database for this CVE.

MODIFIED

Vulnerability data or affected products updated.

PUBLISHED

Vulnerability first announced in NVD.

Attack Vector Matrix

Access Vector NETWORK
Complexity LOW
Privileges N/A
Interaction NONE
CVSS Vector String CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected Stack

No specific products linked.