Vulnerability in Apache HTTP Server
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.462 (98.8th percentile), scored .
Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 99th percentile — 98.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.462 · newest: 0.462 · change: 0.000
Affected products
- Apache HTTP Server
- Apache Software Foundation HTTP Server — versions Apache HTTP Server 2.4 2.4.17 to 2.4.48
- Oracle Secure Backup
- Oracle Zfs Storage Appliance Kit — versions 8.8
- Tenable Tenable.sc
- Debian Linux — versions 10.0
- Fedoraproject Fedora — versions 34, 35
Public proof-of-concept exploits
References
- portswigger.net/research/http2 (Exploit, Third Party Advisory)
- github.com/apache/httpd/commit/ecebcc035ccd8d0e2984fe41420d9e944f456b3c.patch (Patch)
- lists.apache.org/thread.html/re4162adc051c1a0a79e7a24093f3776373e8733abaff57253… (mailing-list, Patch)
- lists.apache.org/thread.html/ree7519d71415ecdd170ff1889cab552d71758d2ba2904a17d… (mailing-list, Patch)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory, Third Party Advisory)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory, Third Party Advisory)
- tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-h… (vendor-advisory, Third Party Advisory)
- www.oracle.com/security-alerts/cpujan2022.html (Patch, Third Party Advisory)
- security.netapp.com/advisory/ntap-20210917-0004/ (Third Party Advisory)
- www.tenable.com/security/tns-2021-17 (Third Party Advisory)
Frequently asked questions
- What is CVE-2021-33193?
- CVE-2021-33193 is a high-severity vulnerability in Apache HTTP Server. CVSS score: 7.5/10. Published 2021-08-16.
- How severe is CVE-2021-33193?
- High severity. CVSS v3 base score is 7.5 out of 10.
- Is CVE-2021-33193 known to be exploited?
- 14 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.