CVE-2021-41773
HighExploitedPublic exploitAn attacker could use a path traversal attack to map URLs to files outside the directories configured by Alias-like directives.
Published Nov 12, 2021 · Updated Sep 8, 2026 · Also known as ALPINE-CVE-2021-41773, BIT-apache-2021-41773, DEBIAN-CVE-2021-41773, TR-21-0809, TR-21-0813, TR-21-0846, TR-21-0918
Key Facts
Patch immediately- CVE-2021-41773 is a high-severity vulnerability (CVSS 7.5 v3.1) affecting HTTP Server (Apache), Cloud Backup (Netapp), Instantis Enterprisetrack (Oracle) and 22 more products.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Sep 29, 2021 and is known to be used in ransomware campaigns. Public exploit code is available.
- EPSS estimates a 100% probability of exploitation in the next 30 days.
- Fixed versions are available, including apache 2.4.50, apache 2.4.50-1, apache2 2.4.50-1.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS (30-day exploit likelihood)
100%
Higher than 99.9% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings, used by ransomware
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2021-41773 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
Description
A flaw was found in a change made to path normalization in Apache HTTP Server 2.4.49. An attacker could use a path traversal attack to map URLs to files outside the directories configured by Alias-like directives. If files outside of these directories are not protected by the usual default configuration "require all denied", these requests can succeed. If CGI scripts are also enabled for these aliased pathes, this could allow for remote code execution. This issue is known to be exploited in the wild. This issue only affects Apache 2.4.49 and not earlier versions. The fix in Apache HTTP Server 2.4.50 was found to be incomplete, see CVE-2021-42013.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Nov 3, 2021 | Nov 17, 2021 | Known |
| Industry KEV feed | Sep 29, 2021 | Nov 17, 2021 | Known |
| CIRCL KEV | Nov 3, 2021 | Nov 17, 2021 | Known |
| ENISA EUVD | Nov 3, 2021 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
63 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| HTTP ServerApache | 2.4.49, >= Apache HTTP Server 2.4 2.4.49 | n/a |
| Cloud BackupNetapp | See advisory | n/a |
| Instantis EnterprisetrackOracle | 17.1, 17.2, 17.3 | n/a |
| FedoraFedoraproject | 34, 35 | n/a |
| apachearch | >= 2.4.49 | 2.4.50-1 |
Patched Releases
apache
2.4.50, 2.4.50-1
apache2
2.4.50-1, 2.4.50-r0, 2.4.51-1.1
httpd
2.4.51-1, 2.4.51-1.amzn2, 2.4.51-1.ph4
httpd-devel
2.4.51-1.amzn2, 2.4.51-1.ph4
httpd-docs
2.4.51-1.ph4
httpd-filesystem
2.4.51-1.amzn2
httpd-manual
2.4.51-1.amzn2
httpd-tools
2.4.51-1.amzn2, 2.4.51-1.ph4
httpd24
2.4.51-1.94.amzn1
httpd24-devel
2.4.51-1.94.amzn1
httpd24-manual
2.4.51-1.94.amzn1
httpd24-tools
2.4.51-1.94.amzn1
mod_ldap
2.4.51-1.amzn2
mod_md
2.4.51-1.amzn2
mod_proxy_html
1:2.4.51-1.amzn2
mod_session
2.4.51-1.amzn2
mod_ssl
1:2.4.51-1.amzn2
mod24_ldap
2.4.51-1.94.amzn1
mod24_md
2.4.51-1.94.amzn1
mod24_proxy_html
1:2.4.51-1.94.amzn1
mod24_session
2.4.51-1.94.amzn1
mod24_ssl
1:2.4.51-1.94.amzn1
rootio-apache2
2.4.50-1
Timeline
Added to Industry KEV feed
Sep 29, 2021
Added to CISA KEV
Nov 3, 2021
Added to CIRCL KEV
Nov 3, 2021
Added to ENISA EUVD
Nov 3, 2021
Publicly disclosed
Nov 12, 2021
Last updated
Sep 8, 2026
Weakness Type
- CWE-22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
References
- advisoryhttps://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-41773
- advisoryhttps://httpd.apache.org/security/vulnerabilities_24.html
- advisoryhttps://nvd.nist.gov/vuln/detail/CVE-2021-42013
- advisoryhttps://security.alpinelinux.org/vuln/CVE-2021-41773
- advisoryhttps://securityboulevard.com/2021/10/apache-web-server-path-traversal-and-file-disclosure-vulnerability-cve-2021-41773/
FAQ
Common Questions.
A flaw was found in a change made to path normalization in Apache HTTP Server 2.4.49.
Affected: HTTP Server (Apache) versions 2.4.49, >= Apache HTTP Server 2.4 2.4.49; Cloud Backup (Netapp); Instantis Enterprisetrack (Oracle) versions 17.1, 17.2, 17.3, among others. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Sep 29, 2021 and is known to be used in ransomware campaigns.
Yes. It was added on Nov 3, 2021 with a federal remediation due date of Nov 17, 2021.
Public exploit code is available.
Fixed versions are available, including apache 2.4.50, apache 2.4.50-1, apache2 2.4.50-1.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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