NVD / CVE Program· CNA apache

CVE-2021-41773: Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49

Noroxi assessment

Priority: Now (action score 99/100)

CISA has confirmed exploitation in the wild (Nov 3, 2021); it is known to be used in ransomware campaigns. Remediation deadline for US federal agencies: Nov 17, 2021.
A ready-made attack module is public (Metasploit, Nuclei); exploiting it takes no special expertise.
Probability of exploitation in the next 30 days: 99.9% (FIRST EPSS); higher than 99.9% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
Fixed version: apache2 (Alpine:v3.11) 2.4.50-r0; apache2 (Debian:12) 2.4.50-1; apache2 (openSUSE:Tumbleweed) 2.4.51-1.1.
Mentioned 4 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Patch today or shut off access. Upgrade to apache2 (Alpine:v3.11) 2.4.50-r0; apache2 (Debian:12) 2.4.50-1; apache2 (openSUSE:Tumbleweed) 2.4.51-1.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · CISA KEV · FIRST EPSS

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.

CriticalCVSS 9.8 · v3.1KEVWeaponized Fix available

Published: Oct 5, 2021
Updated: Jun 17, 2026
EPSS: 99.9% · 99th percentile
CWE: CWE-22

Report tools

JSON

Action score

Now

Patch today or shut off access.

CVSS: 39 / 40 · 9.8 / 10
CISA KEV: 30 / 30 · Listed
EPSS: 30 / 30 · 99.9%

CISA SSVC decision

Exploitation: active
Automatable: yes
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

Actively exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on Nov 3, 2021. That signals real attacks, not theory.

Remediation deadline for US federal agencies: Nov 17, 2021.

Known to be used in ransomware campaigns.

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In CISA KEV: exploitation in the wild confirmed
Weaponized exploit exists
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
apache	http server	cpe:2.3:a:apache:http_server
fedoraproject	fedora	cpe:2.3:o:fedoraproject:fedora
oracle	instantis enterprisetrack	cpe:2.3:a:oracle:instantis_enterprisetrack
netapp	cloud backup	cpe:2.3:a:netapp:cloud_backup

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Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

apache http server2.4.49

Versions reported by the vendor

Affected version ranges reported by the assigning authority (apache). Independent of NVD's CPE analysis and usually ahead of it.

Apache Software Foundation Apache HTTP Server
- Apache HTTP Server 2.4 2.4.49affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Alpine:v3.11	apache2	before 2.4.50-r0	2.4.50-r0
Debian:12	apache2	before 2.4.50-1	2.4.50-1
openSUSE:Tumbleweed	apache2	before 2.4.51-1.1	2.4.51-1.1

Same product

apache: all records

Other highest-scoring records for the same primary product.

CVE-2021-42013Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773)KEV
99Now
CVE-2024-38475Apache HTTP Server weakness in mod_rewrite when first segment of substitution matches filesystem path.KEV
96Now
CVE-2019-0211In Apache HTTP Server 2.4 releases 2.4.17 to 2.4.38, with MPM event, worker or prefork, code executing in less-privileged child processes orKEV
81Now

Published before and after this one in the same product

← EarlierCVE-2021-39275Sep 16, 2021 · ap_escape_quotes buffer overflow
51Plan
← EarlierCVE-2021-41524Oct 5, 2021 · null pointer dereference in h2 fuzzing
38Monitor
Later →CVE-2021-44224Dec 20, 2021 · Possible NULL dereference or SSRF in forward proxy configurations in Apache HTTP Server 2.4.51 and earlier
57Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
alpine:apache2	2.4.50-r0 · Alpine:v3.11	Package registry (OSV)
debian:apache2	2.4.50-1 · Debian:12	Package registry (OSV)
opensuse:apache2	2.4.51-1.1 · openSUSE:Tumbleweed	Package registry (OSV)

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Evidence

Metasploit module ×2
Exploit-DB entry ×2
Nuclei detection template ×2
Proof-of-concept repository on GitHub ×50

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
Source	Kind	Date
Exploit-DB entry	webapps	2021-10-06
Exploit-DB entry	webapps	2021-11-11
Metasploit module	auxiliary/scanner/http/apache_normalize_pathApache 2.4.49/2.4.50 Traversal RCE scannerauxiliary	2021-05-10
Metasploit module	exploit/multi/http/apache_normalize_path_rceApache 2.4.49/2.4.50 Traversal RCEexploit	2021-05-10
Nuclei detection template	Nuclei template CVE-2021-41773	—
Nuclei detection template	Nuclei template CVE-2021-42013	—
Proof-of-concept repository on GitHub	stars:38	2021-10-05
Proof-of-concept repository on GitHub	stars:8	2021-10-05
Proof-of-concept repository on GitHub	stars:9	2021-10-05
Proof-of-concept repository on GitHub	stars:17	2021-10-05
Proof-of-concept repository on GitHub	stars:53	2021-10-05
Proof-of-concept repository on GitHub	stars:1	2021-10-05

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

MetasploitMay 10, 2021-148 d
First PoCOct 5, 2021same day
PublishedOct 5, 2021
CISA KEVNov 3, 2021+29 d
TodayNov 2, 2026+1855 d

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Ash Daulton along with the cPanel Security Team

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

TR-21-0918 · Nov 12, 2021(Apache HTTP Server Güvenlik Zafiyeti)
TR-21-0846 · Oct 19, 2021(Apache Güncellemesi)
TR-21-0813 · Oct 7, 2021(Apache Server Güvenlik Güncellemesi) - CVE Kodları ve Referanslar Güncellenmiştir!
TR-21-0809 · Oct 6, 2021(Apache Server Güvenlik Zafiyeti)

All national notices →

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: high · data or configuration can be modified
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

Weakness class (CWE)

CWE-22 · Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

nvd-primary

Root cause

A user-supplied file name is joined with the allowed directory, but the result is never checked to confirm it is still inside that directory.

The bug in code

The whole CWE-22 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1const file = path.join(ROOT, req.query.name);
2res.sendFile(file);

Fixed

1const file = path.resolve(ROOT, req.query.name);
2if (!file.startsWith(ROOT + path.sep)) {
3  return res.sendStatus(400);
4}
5res.sendFile(file);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

—

Change log

Fix✗ → ✓Sep 28, 2026, 10:44 PM UTC

For records you follow, these changes also arrive as notifications. →

References

www.openwall.com/lists/oss-security/2021/10/05/2

Show all references (19 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records

Noroxi analysis

What does it mean in your environment?

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Data sources and verification

CNA: apache

CVE.org (CNA)Oct 21, 2025, 11:25 PM UTC
CISA ADPOct 21, 2025, 11:25 PM UTC
NVDJun 17, 2026, 12:08 AM UTC
FIRST EPSSOct 14, 2026, 12:00 AM UTC
OSV / GHSANov 2, 2026, 3:17 AM UTC
Exploit-DBNov 2, 2026, 3:17 AM UTC
MetasploitNov 2, 2026, 3:17 AM UTC
NucleiNov 2, 2026, 3:17 AM UTC
PoC-in-GitHubNov 2, 2026, 3:17 AM UTC

Each line is when that source was last processed for this record.

CVE-2021-41773: Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49

Noroxi assessment

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Affected systems

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Affected versions

Versions reported by the vendor

Package-level exposure

Same product

Remediation

Which version to upgrade to

Exploit status

Research context

Timeline

Patch and commit links

Credits

Variant candidates

Chain candidates

National notice (Türkiye Cybersecurity Directorate / USOM)

Technical details

Attack conditions

If successful

Root cause

The bug in code

Attack context

Change log

References