CVE-2021-41773Known exploitationPublic exploitNetwork attack vector

File disclosure and code execution via path normalization

Published Oct 5, 2021 · Updated Oct 21, 2025

Path traversal in Apache HTTP Server 2.4.49 allows remote attackers to read files or execute code through crafted URL paths. A regression in path normalization fails to reject encoded dot segments before Alias-like URL mappings resolve them outside the configured directory. File reads require missing default Require all denied protection; code execution additionally requires CGI scripts for the alias.

CVSS severity9.8
Critical
EPSS probability99.99%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in Apache HTTP Server 2.4.49 allows remote attackers to read files or execute code through crafted URL paths. A regression in path normalization fails to reject encoded dot segments before Alias-like URL mappings resolve them outside the configured directory. File reads require missing default Require all denied protection; code execution additionally requires CGI scripts for the alias.

The record

CVE
CVE-2021-41773
Published
Oct 5, 2021
Updated
Oct 21, 2025
Vendor
The Apache Software Foundation
Product
Apache HTTP Server
Classifications
CWE-22, CAPEC-126, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 5, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2021Exploitation reportedCISA Known Exploited Vulnerabilities entry
  3. Oct 21, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Apache HTTP Server 2.4 2.4.49

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache HTTP Serverversion=Apache HTTP Server 2.4 2.4.49

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
4.3NVDAV:N/AC:M/Au:N/C:P/I:N/A:N
9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CAPEC-126Path Traversal
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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