Threats / Apache / CVE-2021-41773
CVE-2021-41773
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-09-19
Apache HTTP Server vulnerability
Apache HTTP Server path traversal vulnerability allowing remote code execution when Alias directives lack proper access controls or CGI is enabled. Actively exploited with ransomware deployment.
Verdict
Today item, not a backlog item.
Critical path traversal flaw enabling unauthenticated remote code execution on vulnerable Apache servers. Initial patch insufficient; CVE-2021-42013 addresses bypass. High real-world exploitation activity with ransomware campaigns documented.
CISA KEV Yes · 2021-11-035Ransomware use Flagged5EPSS 0.99992 (verify live)6Exploit Weaponized · public PoC7CVSS 7.5 (CISA)4CISA SSVC Exploitation: active · Automatable: yes · Impact: total4
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Fully weaponized — public exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
383 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.99992 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N) · Affected: Apache, HTTP Server. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-22 Path Traversal — weakness family: Path traversal / file.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: yes · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 29 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
Public exploit available
Public exploit tooling is catalogued for this CVE (a functional/weaponized public exploit). Catalog entries: Metasploit module, nuclei template. We link the catalog page(s) only — no payload or code is hosted or restated here.Link, never host — the catalog page is the source; basicsecurity.net does not redistribute payloads.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft HTTP requests with path traversal sequences to access files outside configured Alias directories.
Business
Attacker gains unauthorized file system access on the web server.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I locate and execute CGI scripts or write malicious scripts to arbitrary locations on the server.
Business
Attacker achieves remote code execution with web server privileges.
3
Lateral reach — past segmentation narrative 3
Attacker
I establish persistence and deploy ransomware or data exfiltration payloads across the infrastructure.
Business
Organization experiences operational shutdown, data loss, and financial extortion demands.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05
Coverage & confidence
— what we know, and what we don’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by apacheCNA
Credited with finding itThis issue was reported by Ash Daulton along with the cPanel Security Teamunspecified
Found an error? Propose a correction.
A correction is a cited counter-claim — it must cite a source,
gets reviewed by a second human, and is never auto-applied. See the
correction convention and our identity
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