Exploited CVEs / Apache / CVE-2021-41773
CVE-2021-41773
Apache HTTP Server Path Traversal Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted, and the vulnerability is known to be used in ransomware campaigns. Federal agencies were required to remediate by 2021-11-17 (that deadline has passed); treat that date as the outer bound for your own environment. Check the vendor security advisory for the fix.
Actively exploited Apache HTTP Server vulnerability, Critical severity, CVSS 9.8. Added to the CISA KEV catalog 2021-11-03.
Risk summary
Updated July 28, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.
Senserva AI Opinion for CVE-2021-41773
This path traversal flaw in Apache HTTP Server 2.4.49 turns to remote code execution when CGI scripts are enabled or when files outside Alias directories are not under default require all denied, and the incomplete original patch made it especially dangerous. Anyone running an internet-facing Apache HTTP Server with mod_cgi or loosened directory access is exposed, and this is confirmed in CISA KEV with a 100 percent EPSS score and documented ransomware use. Exploitation is trivial and public, so unpatched servers are being hit rather than merely at risk.
Do this: Identify all Apache HTTP Server instances, confirm they are not on 2.4.49, verify directories use require all denied, and disable unneeded CGI while applying the vendor fixed release today.
AI-generated from public data, 2026-07-23. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2021-41773
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for CVE-2021-41773
Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.
CISA required action
Federal (BOD 22-01) remediation due date: 2021-11-17 (past due).
Apply updates per vendor instructions.
Official fix for CVE-2021-41773
Check the vendor's security advisory channel for the patched HTTP Server versions and workarounds.
Common questions about CVE-2021-41773
Is CVE-2021-41773 actively exploited?
Yes. CVE-2021-41773 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2021-11-03, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 100%. CISA also reports it is known to be used in ransomware campaigns.
What is the CISA deadline and required action for CVE-2021-41773?
CISA set the federal (BOD 22-01) remediation due date at 2021-11-17, which has passed; treat any unremediated system as overdue. The verbatim required action: Apply updates per vendor instructions.
What fixes CVE-2021-41773?
Check the vendor's security advisory for the patched HTTP Server versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.
Can I ask my own AI about CVE-2021-41773?
Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2021-41773's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).
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Authoritative references
Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.
