KEV Intelligence

Vulnerability report

Active exploitation observed Confirmed confidence In CISA KEV

CVE-2021-41773

Apache HTTP Server Path Traversal

Apache Software Foundation / Apache HTTP Server · Apache HTTP Server 2.4 2.4.49

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Severity
CVSS 7.5 · High
Confidence
Confirmed
Exploit status
Observed in sensors
EPSS
100.0%
First observed
29 Jun 2026
Last observed
19 Aug 2026

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2021-41773 is an unauthenticated vulnerability affecting Apache Software Foundation Apache HTTP Server. A flaw was found in a change made to path normalization in Apache HTTP Server 2.4.49. An attacker could use a...

Is it exploited?

Yes. KEV Intelligence sensors observed exploitation attempts with confirmed confidence.

Who is affected?

Apache Software Foundation / Apache HTTP Server apache http server 2.4 2.4.49.

What should we do?

Patch immediately, validate internet-facing exposure, and monitor for matching requests.

Overview

A flaw was found in a change made to path normalization in Apache HTTP Server 2.4.49

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.

Vendor Product Affected Status
Apache Software Foundation Apache HTTP Server Apache HTTP Server 2.4 2.4.49 Affected
View vendor advisory (opens in new tab)
Published
05 Oct 2021
Exploitation Reported
03 Nov 2021
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

metasploit ransomware cisa apache malware nuclei_scanner

CVE References

Exploitation evidence

Why KEV Intelligence marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

CISA

Recorded 03 Nov 2021

Independent exploitation attestation added to the KEV Intelligence record.

Active exploitation observed

KEV Intelligence sensor

First observed 09 Jul 2026

First-party sensor telemetry confirms matching exploitation attempts.

Used in malware

CISA

Recorded 03 Nov 2021

Malware families have been linked to exploitation of this CVE.

Proof of concept available

GitHub

Recorded 05 Oct 2021

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.

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Source Added
CISA First 2021-11-03 00:00 UTC
KEV Intelligence 2026-07-16 15:07 UTC

Operational indicators for this CVE are listed under Detection.

Sensor telemetry

First-party evidence of exploitation activity

Aggregate observations show the scale, recency, and distribution of activity without overstating sparse data.

3,178

Attempts observed

565

Unique attacker IPs

53

Attacker countries

AE · AR · BD · BE · BG · BR · CA · CH · CN · CO · DE · DO · ES · FI · FR · GB · HK · ID · IE · IL · IN · IR · JP · KR · KZ · LU · LV · LY · MW · MY · NG · NL · NP · PA · PE · PK · PL · PT · RS · RU · SA · SC · SE · SG · SO · TH · TR · TW · UA · US · UZ · VN · ZM

33

Sensors observed

Exploitation attempts over the last 53 days

Daily events observed by KEV Intelligence sensors

Updated 19 Aug 2026

0
24
69
70
67
465
103
81
78
89
134
135
228
264
182
206
186
198
211
208
184
250
206
239
192
116
86
75
100
86
66
105
112
94
98
94
84
82
87
99
226
85
85
73
90
96
95
110
88
87
93
90
59
28 Jun 9 Jul 20 Jul 31 Jul 19 Aug

First observed 29 Jun 2026 · Last observed 19 Aug 2026

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Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
17
User-Agents
24

Raw values available in Pro and Enterprise.

Virtual patch status

No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

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Attacker IP Indicators

Attacker IP indicators observed · available in Pro and Enterprise.

Sensor-derived attacker IP indicators are available to Pro and Enterprise accounts under Detection and through the Pro API.

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Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Metasploit https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/multi/http/apache_normalize_path_rce.rb 28 Apr 2025
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-41773.yaml 25 Apr 2025

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

100.0%

Weaknesses

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') CWE-22

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

thehackersbrain/CVE-2021-41773

github · Created 2022-03-12 21:24:55 UTC · 107 stars · AI assessment 90%

Apache2 2.4.49 - LFI & RCE Exploit - CVE-2021-41773

blasty/CVE-2021-41773

github · Created 2021-10-06 07:17:05 UTC · 208 stars · AI assessment 90%

CVE-2021-41773 playground

Ls4ss/CVE-2021-41773_CVE-2021-42013

github · Created 2021-10-06 02:28:41 UTC · 21 stars · AI assessment 90%

Apache HTTP Server 2.4.49, 2.4.50 - Path Traversal & RCE

lorddemon/CVE-2021-41773-PoC

github · Created 2021-10-05 23:53:48 UTC · 37 stars · AI assessment 90%

iilegacyyii/PoC-CVE-2021-41773

github · Created 2021-10-05 17:30:43 UTC · 47 stars · AI assessment 90%

Apache 2.4.49 - Path Traversal and Remote Code Execution

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. Observed by KEV Intelligence sensors

    Evidence-backed exploitation signal

  2. Indicators of compromise added (1048)

    Indicators of compromise recorded

  3. Metasploit module available

    Exploit module available

  4. Nuclei template available

    Scanner coverage available

  5. Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  6. First public exploitation report

    Exploit observed in malware

  7. Public PoC available

    Public proof-of-concept code published

  8. CVE published

    Vulnerability disclosed publicly

  9. CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2021-41773

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2021-41773",
  "confidence": "Confirmed",
  "cvss_score": 7.5,
  "cvss_estimated": false,
  "epss_score": 0.99992,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": true
  },
  "sensor_telemetry": { "attempts": 3178, "sensors": 33 }
}

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