CVE-2021-33193
Request splitting via HTTP/2 method injection and mod_proxy
HIGH
7.5
CVSS Score
Published: August 16, 2021 at 12:00 AM UTC
Updated: June 17, 2026 at 03:54 AM UTC
6 products affected across 5 vendorsDebian LinuxFedoraHTTP Server
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Severity
HIGH7.5
Exploit prediction
EPSS 46%
Description
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.
Affected
Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.
v ≤ 2.4.482.4.17 ≤ v < 2.4.49
Affected range stops below 2.4.49, so it looks safe — our inference, not a vendor statement
Debian Linux· Debiandrupal
95%v < 18.1.0.1.0
Affected range stops below 18.1.0.1.0, so it looks safe — our inference, not a vendor statement
Tenable.Sc· Tenabledrupal
95%v ≤ 5.19.1
Remediation
No guide yetNo remediation guidance has been written for this CVE yet. What the record does show:
Patch and advisory references
- 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.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DSM6UWQICBJ2TU727RENU3HBKEAFLT6T/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EUVJVRJRBW5QVX4OY3NOHZDQ3B3YOTSG/
References (13)
Mailing ListThird Party Advisory
Source: [email protected]
https://lists.debian.org/debian-lts-announce/2023/03/msg00002.htmlVendor AdvisoryThird Party Advisory
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DSM6UWQICBJ2TU727RENU3HBKEAFLT6T/Vendor AdvisoryThird Party Advisory
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EUVJVRJRBW5QVX4OY3NOHZDQ3B3YOTSG/Vendor AdvisoryThird Party Advisory
Source: [email protected]
https://security.gentoo.org/glsa/202208-20CVSS
- Attack Vector
- NETWORK
- Complexity
- LOW
- Privileges
- NONE
- User Interaction
- NONE
- Scope
- UNCHANGED
- Confidentiality
- NONE
- Integrity
- HIGH
- Availability
- NONE
Vector?
Quick Info
StatusANALYZED
CWE
NVD-CWE-Other
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