How severe is CVE-2021-41773?

CVE-2021-41773 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-41773 being actively exploited?

Yes. CVE-2021-41773 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2021-11-03, which means active exploitation has been confirmed. It should be prioritised for remediation.

What products are affected by CVE-2021-41773?

CVE-2021-41773 primarily affects Apache Http Server. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-41773?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.

Does CVE-2021-41773 have an EU (EUVD) identifier?

Yes. CVE-2021-41773 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-28781. It is also flagged as exploited in the EUVD (since 2021-11-03).

When was CVE-2021-41773 published?

CVE-2021-41773 was published on 2021-10-05 and last updated on 2026-06-17.

CVE-2021-41773

CVE-2021-41773 is a critical-severity vulnerability in Apache Http Server with a CVSS 3.x base score of 9.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2021-11-03). The underlying weakness is classified as CWE-22.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 4.3
EPSS exploit prediction: 100% (100th percentile)
Actively exploited: Yes — listed in CISA KEV (added 2021-11-03)
EU (EUVD) id: EUVD-2021-28781
EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2021-11-03)
Weakness: CWE-22
Affected product: Apache Http Server
Published: 2021-10-05
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-41773?: 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.
How severe is CVE-2021-41773?: CVE-2021-41773 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-41773 being actively exploited?: Yes. CVE-2021-41773 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2021-11-03, which means active exploitation has been confirmed. It should be prioritised for remediation.
What products are affected by CVE-2021-41773?: CVE-2021-41773 primarily affects Apache Http Server. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-41773?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.
Does CVE-2021-41773 have an EU (EUVD) identifier?: Yes. CVE-2021-41773 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-28781. It is also flagged as exploited in the EUVD (since 2021-11-03).
When was CVE-2021-41773 published?: CVE-2021-41773 was published on 2021-10-05 and last updated on 2026-06-17.

References

Affected products (7)

cpe:2.3:a:apache:http_server:2.4.49:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
cpe:2.3:a:oracle:instantis_enterprisetrack:17.1:*:*:*:*:*:*:*
cpe:2.3:a:oracle:instantis_enterprisetrack:17.2:*:*:*:*:*:*:*
cpe:2.3:a:oracle:instantis_enterprisetrack:17.3:*:*:*:*:*:*:*
cpe:2.3:a:netapp:cloud_backup:-:*:*:*:*:*:*:*

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Threat intelligence

Threat-intel indicators referencing this CVE:

143.110.141.86 (ipv4-addr)
103.215.75.19 (ipv4-addr)