Threats / Apache / CVE-2021-42013
CVE-2021-42013
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Apache HTTP Server vulnerability
Apache HTTP Server path traversal vulnerability allowing remote code execution through incomplete patching of CVE-2021-41773, exploitable when Alias directives lack proper access controls or CGI is enabled.
Verdict
Today item, not a backlog item.
Critical path traversal flaw enabling unauthenticated remote code execution on affected Apache servers. Active exploitation in ransomware campaigns demonstrates severe real-world risk. Requires immediate patching regardless of configuration.
CISA KEV Yes · 2021-11-033Ransomware use Flagged3EPSS 0.99964 (verify live)4Exploit Weaponized · public PoC5
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
719 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 0.99964 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Apache, HTTP Server. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-22 Path Traversal — weakness family: Path traversal / file.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
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 requests using path traversal sequences to access files outside configured Alias directories.
Business
Attacker gains unauthorized file system access, bypassing intended directory restrictions.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I locate and execute CGI scripts or upload malicious code to writable locations accessible through traversal.
Business
Remote code execution achieved with web server privileges, enabling full system compromise.
3
Lateral reach — past segmentation narrative 3
Attacker
I establish persistence and deploy ransomware or data exfiltration payloads across the infrastructure.
Business
Operations disrupted, data encrypted or stolen, ransom demanded, regulatory obligations triggered.
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