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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 usu…

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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.
CVSS 7.5 (HIGH) KEV: KNOWN CATALOG

Attention and evidence

HYPE SCORE
0.0/10
REALITY · THREAT PRIORITY
8.6/10
General review priority; not probability

Evidence confidence: Exploitation recorded

Why this priority?
  • Recorded exploitation baseline: +7.00
  • Technical severity: CVSS 7.5: +1.12
  • Fresh EPSS: 99.99%: +0.50

General review priority, not probability, victim count or asset-specific risk. A range covers missing CVSS/EPSS inputs within the current evidence state.

Sources: 22 documents and public datasets.

Hype components

Headline sample (25%)
0/100
Press, 30 days (60%)
0/100
Grounded branding (15%)
0/100
HYPE TOTAL0/100

Sources and documents

The Hacker News
Press · 17 Jul 2025, 07:00 · Hackers Exploit Apache HTTP Server Flaw to Deploy Linuxsys Cryptocurrency Miner - The Hacker News
Rescana
Press · 06 Oct 2024, 07:00 · Exploiting CVE-2021-41773: Critical Path Traversal Vulnerability in Apache HTTP Server 2.4.49 - Rescana
Cybernews
Press · 05 Oct 2023, 07:00 · Zero-day bugs: what they are and how to defend against them - Cybernews
Bitsight
Press · 22 Dec 2021, 08:00 · Bitsight Research Roundup 2021 - Bitsight
www.trendmicro.com
Press · 21 Dec 2021, 08:00 · How to detect Apache HTTP Server Exploitation - www.trendmicro.com
See all 22 source documents
www.trendmicro.com
Press · 21 Dec 2021, 08:00 · How to detect Apache HTTP Server Exploitation - www.trendmicro.com
www.trendmicro.com
Press · 21 Dec 2021, 08:00 · How to detect Apache HTTP Server Exploitation - www.trendmicro.com
www.trendmicro.com
Press · 03 Dec 2021, 08:00 · Vulnerabilities Exploited for Monero Mining Malware Delivered via GitHub, Netlify - www.trendmicro.com
Bitsight
Press · 03 Nov 2021, 07:00 · Bitsight Apache Risk Analysis Highlights Need To Address CISA “Known Vulnerabilities” - Bitsight
Qualys
Press · 27 Oct 2021, 07:00 · Apache HTTP Server Path Traversal & Remote Code Execution (CVE-2021-41773 & CVE-2021-42013) - Qualys
wiz.io
Press · 08 Oct 2021, 07:00 · Protecting cloud environments from the new critical Apache HTTP Server vulnerability - wiz.io
Arctic Wolf
Press · 08 Oct 2021, 07:00 · CVE-2021-41773 & CVE-2021-42013 - Arctic Wolf
Cloudflare Blog
Press · 08 Oct 2021, 07:00 · Helping Apache Servers stay safe from zero-day path traversal attacks (CVE-2021-41773) - Cloudflare Blog
GreyNoise
Press · 07 Oct 2021, 07:00 · Path Traversal and Remote Code Execution in Apache HTTP Server, CVE-2021-41773 - GreyNoise
Akamai
Press · 07 Oct 2021, 07:00 · Mitigating CVE-2021-41773: Apache HTTP Server Path Traversal - Akamai
BleepingComputer
Press · 07 Oct 2021, 07:00 · Apache emergency update fixes incomplete patch for exploited bug - BleepingComputer
Sophos
Press · 06 Oct 2021, 07:00 · Apache web server zero-day bug is easy to exploit – patch now! - Sophos
BleepingComputer
Press · 06 Oct 2021, 07:00 · Actively exploited Apache 0-day also allows remote code execution - BleepingComputer
TechTarget
Press · 06 Oct 2021, 07:00 · Apache HTTP Server vulnerability under active attack - TechTarget
Rapid7
Press · 06 Oct 2021, 07:00 · Apache HTTP Server CVE-2021-41773 Exploited in the Wild - Rapid7
The Hacker News
Press · 05 Oct 2021, 07:00 · Apache Warns of Zero-Day Exploit in the Wild — Patch Your Web Servers Now! - The Hacker News
Qualys
Press · 23 Nov 2011, 08:00 · Apache HTTP Server Reverse Proxy/Rewrite URL Validation Issue - Qualys

Score evolution

● Hype   ● Reality

Earlier evidence-support scores are retained in history; this chart shows only the current priority definition.

First record: hype 0.0 · reality 8.6 (2026-11-02 15:12). The curve appears once the score changes.

Public exploit evidence

36

Public exploit entries / repo candidates

See 30 repos with metrics
RepositoryStarsForksLanguageUpdated
iilegacyyii/PoC-CVE-2021-417735338Python24 Nov 2021, 12:57
lorddemon/CVE-2021-41773-PoC3921Python06 Oct 2021, 15:37
ZephrFish/CVE-2021-41773-PoC1711Python30 Jul 2026, 13:40
blackn0te/Apache-HTTP-Server-2.4.49-2.4.50-Path-Traversal-Remote-Code-Execution130Python22 Aug 2025, 10:05
itsecurityco/CVE-2021-41773126Dockerfile07 Oct 2022, 23:37
asaotomo/CVE-2021-42013-Apache-RCE-Poc-Exp102Python24 Dec 2021, 07:38
aqiao-jashell/CVE-2021-4177391Go15 Aug 2025, 03:49
creadpag/CVE-2021-41773-POC85Lua28 Dec 2022, 17:49
aqiao-jashell/py-CVE-2021-4177370Python02 Nov 2022, 09:26
TishcaTpx/POC-CVE-2021-4177363Python05 Oct 2021, 21:29
habibiefaried/CVE-2021-41773-PoC34Shell06 Oct 2021, 05:39
HxDDD/CVE-PoC30—20 Apr 2022, 00:23
superzerosec/CVE-2021-4177331Python11 Oct 2021, 22:24
iosifache/ApacheRCEEssay20TeX13 May 2022, 06:10
Soliux/CVE-2021-4177320Python11 Nov 2021, 15:11
ashique-thaha/CVE-2021-41773-POC11—20 Mar 2025, 18:34
im2sinister/CVE-2021-4177310Python15 Jul 2026, 04:42
kubota/POC-CVE-2021-4177310Python16 Nov 2021, 20:42
shellreaper/CVE-2021-4177310Python12 Nov 2021, 00:03
vinhjaxt/CVE-2021-41773-exploit11JavaScript08 Oct 2021, 04:55
0xc4t/CVE-2021-4177300Dockerfile27 Aug 2024, 11:37
blu3ming/PoC-CVE-2021-4177300Python02 Jul 2025, 21:30
fxdyx-a/CVE-2021-41773-POC00—14 Jun 2026, 21:13
gunzf0x/CVE-2021-4177300Python07 Oct 2025, 08:35
Hattan515/POC-CVE-2021-4177301Python07 Oct 2021, 11:42
mah4nzfr/CVE-2021-4177301Shell11 Aug 2025, 14:26
mightysai1997/CVE-2021-41773-PoC00Shell11 Dec 2025, 20:16
sixpacksecurity/CVE-2021-4177300Dockerfile07 Oct 2021, 13:00
TheLastVvV/CVE-2021-4177300Shell23 Oct 2021, 21:50
tr3m0x/CVE-2021-4177300Dockerfile27 Jul 2026, 13:55
Public exploit evidence
Evidence context and dated references

Reality is general threat/review priority, combining observed exploitation, CVSS severity and fresh EPSS. Evidence confidence is separate. This is not calibrated risk, a victim count or an asset-specific assessment. A range reflects missing numeric inputs.

Evidence in context

Confidence in exploitation evidence
Exploitation recorded
Priority basis
Recorded exploitation; CVSS 7.5; EPSS 100.0%
Attention, last 30 days
0 distinct story titles; 0 press documents; 0 publisher domains.
Technical potential
network access, no prior privileges, no user interaction.
Observed activity
Exploitation recorded in CISA KEV.
Known scale
Not quantified.
Evidence confidence basis
Trusted exploitation confirmation

Score evaluated: 2026-11-05 13:58:31.036516+00:00 · EPSS snapshot: 2026-11-05T12:03:04Z

Source event timeline
First press mention
23 Nov 2011, 08:00
Published
05 Oct 2021, 08:40
Added to the CISA KEV catalog
03 Nov 2021, 00:00
Latest press mention
17 Jul 2025, 07:00
Score calculated
05 Nov 2026, 13:58
PoCs on GitHub
36 repositories