CVE-2021-33193

Request splitting via HTTP/2 method injection and mod_proxy

Severity Score

7.5

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

*SSVC

Descriptions

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.

Un método diseñado enviado mediante HTTP/2 omitirá la comprobación y será reenviado por mod_proxy, lo que puede conllevar a la división de peticiones o el envenenamiento de la caché. Este problema afecta a Apache HTTP Server versiones 2.4.17 a 2.4.48.

A NULL pointer dereference was found in Apache httpd mod_h2. The highest threat from this flaw is to system integrity.

*Credits: Reported by James Kettle of PortSwigger

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

High

Availability

None

Attack Vector

Network

Attack Complexity

Low

Authentication

None

Confidentiality

None

Integrity

Partial

Availability

None

* Common Vulnerability Scoring System

SSVC

Decision:-

Exploitation

Automatable

Tech. Impact

* Organization's Worst-case Scenario

Timeline

2021-05-19 CVE Reserved
2021-08-16 CVE Published
2024-05-01 EPSS Updated
2024-08-03 CVE Updated
2024-08-03 First Exploit
---------- Exploited in Wild
---------- KEV Due Date

CWE

CWE-476: NULL Pointer Dereference

CAPEC

References (15)

URL	Tag	Source
https://lists.apache.org/thread.html/re4162adc051c1a0a79e7a24093f3776373e8733abaff57253fef341d%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://lists.apache.org/thread.html/ree7519d71415ecdd170ff1889cab552d71758d2ba2904a17ded21a70%40%3Ccvs.httpd.apache.org%3E	Mailing List
https://lists.debian.org/debian-lts-announce/2023/03/msg00002.html	Mailing List
https://security.netapp.com/advisory/ntap-20210917-0004	Third Party Advisory
https://www.tenable.com/security/tns-2021-17	Third Party Advisory

URL	Date	SRC
https://portswigger.net/research/http2	2024-08-03

URL	Date	SRC
https://github.com/apache/httpd/commit/ecebcc035ccd8d0e2984fe41420d9e944f456b3c.patch	2023-11-07
https://www.oracle.com/security-alerts/cpuapr2022.html	2023-11-07
https://www.oracle.com/security-alerts/cpujan2022.html	2023-11-07

URL	Date	SRC
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DSM6UWQICBJ2TU727RENU3HBKEAFLT6T	2023-11-07
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EUVJVRJRBW5QVX4OY3NOHZDQ3B3YOTSG	2023-11-07
https://security.gentoo.org/glsa/202208-20	2023-11-07
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ	2023-11-07
https://access.redhat.com/security/cve/CVE-2021-33193	2022-10-26
https://bugzilla.redhat.com/show_bug.cgi?id=1966728	2022-10-26

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Apache Search vendor "Apache"		Http Server Search vendor "Apache" for product "Http Server"				>= 2.4.17 <= 2.4.48 Search vendor "Apache" for product "Http Server" and version " >= 2.4.17 <= 2.4.48"		-		Affected
Fedoraproject Search vendor "Fedoraproject"		Fedora Search vendor "Fedoraproject" for product "Fedora"				34 Search vendor "Fedoraproject" for product "Fedora" and version "34"		-		Affected
Fedoraproject Search vendor "Fedoraproject"		Fedora Search vendor "Fedoraproject" for product "Fedora"				35 Search vendor "Fedoraproject" for product "Fedora" and version "35"		-		Affected
Tenable Search vendor "Tenable"		Tenable.sc Search vendor "Tenable" for product "Tenable.sc"				<= 5.19.1 Search vendor "Tenable" for product "Tenable.sc" and version " <= 5.19.1"		-		Affected
Oracle Search vendor "Oracle"		Secure Backup Search vendor "Oracle" for product "Secure Backup"				< 18.1.0.1.0 Search vendor "Oracle" for product "Secure Backup" and version " < 18.1.0.1.0"		-		Affected
Oracle Search vendor "Oracle"		Zfs Storage Appliance Kit Search vendor "Oracle" for product "Zfs Storage Appliance Kit"				8.8 Search vendor "Oracle" for product "Zfs Storage Appliance Kit" and version "8.8"		-		Affected