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ExploitedIn CISA KEVFix available

CVE-2021-42013

Exploitation confirmed. First attested on 2021-11-03 by CISA-ADP, CISA KEV, GCVE · kevintel, GCVE · shadowserver.

  • Published2021-10-07
  • WeaknessCWE-22

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

It was found that the fix for CVE-2021-41773 in Apache HTTP Server 2.4.50 was insufficient. 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 only affects Apache 2.4.49 and Apache 2.4.50 and not earlier versions.

Timeline

dates in UTC
  1. 2021-10-0716:15CVE publishedNVD
  2. 2021-10-13Exploit-DB entryExploit-DB
  3. 2021-11-03Added to the CISA KEV catalogCISA KEV
  4. 2021-11-03Listed as exploited by GCVEGCVE
  5. 2021-11-03Exploitation first reportedCISA KEV
  6. 2025-02-0414:28SSVC exploitation set to activeCISA-ADP

Observed activity

isMalicious corpus · updated 2026-11-03 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-42013?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-42013?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Apache HTTP Server
BranchAffectedFixed in
2.4= 2.4.49no fix published
2.4= 2.4.50no fix published
Oracle instantis enterprisetrack
BranchAffectedFixed in
17.1= 17.1no fix published
17.2= 17.2no fix published
17.3= 17.3no fix published
Fedoraproject fedora
BranchAffectedFixed in
34.x= 34no fix published
35.x= 35no fix published

4 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA1 product

As apache, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • Apache Software Foundation Apache HTTP Server
    Affected
    • = Apache HTTP Server 2.4.49no fix stated
    • = Apache HTTP Server 2.4.50no fix stated

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2022-08-14

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • apacheMageia:8all versions · fixed in 2.4.51-1.mga8
  • apache2openSUSE:Tumbleweedall versions · fixed in 2.4.51-1.1
  • apache2Debian:14all versions · fixed in 2.4.51-1
  • apache2Debian:13all versions · fixed in 2.4.51-1
  • apache2Debian:12all versions · fixed in 2.4.51-1
  • apache2CleanStartall versions · fixed in 2.4.51-r0
  • apache2Alpine:v3.24all versions · fixed in 2.4.51-r0
  • apache2Alpine:v3.23all versions · fixed in 2.4.51-r0

12 more package ranges on OSV.dev

Vendor advisories

  • CVE-2021-42013 Red Hat Product Security

    httpd: path traversal and remote code execution (incomplete fix of CVE-2021-41773)

Full record on NVD

Fix

  1. CISA’s required action: Apply updates per vendor instructions.due 2021-11-17

Advisories and patches

Detection

read 2026-11-03 22:42 UTC
Nuclei template
available
ProjectDiscovery
Exploit-DB
EDB-50406EDB-50446EDB-50512
Exploit-DB
Proof-of-concept repositories
20 repositories, unverifiedandrea-mattioli/apache-exploit-CVE-2021-42013Vulnmachines/cve-2021-42013twseptian/cve-2021-42013-docker-labLayarKacaSiber/CVE-2021-42013TheLastVvV/CVE-2021-42013
PoC-in-GitHub
Metasploit modules
2 modulesexploit/multi/http/apache_normalize_path_rcerank: excellentauxiliary/scanner/http/apache_normalize_pathrank: normalModule metadata: Metasploit Framework, © Rapid7, Inc., BSD-3-Clause.
Metasploit Framework

CISA Known Exploited Vulnerability

Date Added
2021-11-03
Patch Due Date
2021-11-17
Ransomware Use
Known
Required Action
Apply updates per vendor instructions.

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2021-10-07
Last Modified
2026-06-17
NVD status
Analyzed
GitHub Advisory
GHSA-m24x-wx9p-jqmh

Frequently asked questions

What is CVE-2021-42013?

It was found that the fix for CVE-2021-41773 in Apache HTTP Server 2.4.50 was insufficient. 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 only affects Apache 2.4.49 and Apache 2.4.50 and not earlier versions.

Is CVE-2021-42013 actively exploited?

Yes. CVE-2021-42013 is on the CISA Known Exploited Vulnerabilities (KEV) catalog, meaning it has been confirmed as actively exploited in the wild. CISA requires federal agencies to patch by 2021-11-17.

What is the CVSS score for CVE-2021-42013?

CVE-2021-42013 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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