CVE-2021-42013

CRITICALNVD 9.89.8—
EchelonGraph scoreHIGH confidence

Score elevated to 9.8 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 9.8 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, ghsa, nvd
Trending — 3 sources updated this weekExploited in the wild
9.8EG
EchelonGraph verdictMitigate nowTreat as an emergency — this is being exploited.
  • 1 internet-facing service (distinct ip:port) on record running an affected version — derived from Shodan data (© Shodan); a patched service can stay counted while its port stays open
  • Actively exploited in the wild (CISA-KEV)
  • Linked to ransomware campaigns
CISA-KEV: ExploitedEPSS PROB: 100%CVSS: 9.8Exploit: cisa kev · ssvc active · kev ransomware · Metasploit · Exploit-DB (verified) · epss top5pct · epss high · public exploitExposed services: 1

No fix is confirmed yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for the fix.

It was found that the fix for CVE-2021-41773 in Apache HTTP Server 2.4.50 was insufficient. 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 only affects Apache 2.4.49 and Apache 2.4.50 and not earlier versions.

Internet exposure · derived from Shodan data

1 internet-facing service (distinct ip:port) on record running a version that maps to CVE-2021-42013, in our KEV-Exposure radar’s Shodan-derived sample.

across 1 countries (United States)top: http_server🔒 ransomware-linked
See the KEV-Exposure radar →Derived from Shodan data. Shodan data is owned by Shodan, which holds its copyright (© Shodan). EchelonGraph claims no ownership of it or copyright in it. Aggregate, host-redacted.

How it counts: every 12 hours, when Shodan query credits allow, the radar runs one Shodan query per tracked product, reads up to 100 ip:port services per query, and keeps a service when its banner version matches a CISA-KEV or high-EPSS CVE; a service is dropped when neither a search nor a Shodan InternetDB port re-check has refreshed it for 21 days. A re-check that finds the port still listed by Shodan InternetDB refreshes the service without re-reading the banner, so a patched service can stay counted while its port stays open. A count is a banner-version inference over a sample, not an exploit test and not an internet-wide census, and the unit is a service, not a machine: a machine answering on two ports counts twice.

CVSS v3
9.8
EG Score
9.8CRITICALhigh confidence
EG Risk
99
EG Risk 99/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation100% × 40%
Automatability100% × 15%
CISA SSVC: Attend at low mission impact; Act at medium or high.
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation sooner than your standard update timelines at low mission impact and as soon as possible at medium or high, and watch the vendor's advisory for the fix.
EPSS PROB
100%
EPSS %ILE
99th
KEV
⚠ Exploited

CISA SSVCAttend at low mission impact; Act at medium or high.

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation sooner than your standard update timelines at low mission impact and as soon as possible at medium or high, and watch the vendor's advisory for the fix.

Exploitation active (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

October 7, 2021

Last Modified

October 27, 2025

Advisory Details (10)

Auto-updated Oct 1, 2026
No patch confirmed yet.
generic

oss-security - Re: CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773)

http://www.openwall.com/lists/oss-security/2021/10/08/2
generic

oss-security - Re: CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773)

http://www.openwall.com/lists/oss-security/2021/10/08/1
generic

oss-security - CVE-2021-42013: Path Traversal and Remote Code Execution in Apache HTTP Server 2.4.49 and 2.4.50 (incomplete fix of CVE-2021-41773)

http://www.openwall.com/lists/oss-security/2021/10/07/6
generic

Packet Storm - Human Validation

http://packetstormsecurity.com/files/167397/Apache-2.4.50-Remote-Code-Execution.html
generic

Packet Storm - Human Validation

http://packetstormsecurity.com/files/165089/Apache-HTTP-Server-2.4.50-CVE-2021-42013-Exploitation.html
generic

Packet Storm - Human Validation

http://packetstormsecurity.com/files/164941/Apache-HTTP-Server-2.4.50-Remote-Code-Execution.html
generic

Packet Storm - Human Validation

http://packetstormsecurity.com/files/164629/Apache-2.4.49-2.4.50-Traversal-Remote-Code-Execution.html
generic

Packet Storm - Human Validation

http://packetstormsecurity.com/files/164609/Apache-HTTP-Server-2.4.50-Remote-Code-Execution.html
generic

Packet Storm - Human Validation

http://packetstormsecurity.com/files/164501/Apache-HTTP-Server-2.4.50-Path-Traversal-Code-Execution.html
generic

JVN#51106450: Apache HTTP Server vulnerable to directory traversal

http://jvn.jp/en/jp/JVN51106450/index.html

Affected Packages

(17 across 17 ecosystems)
Alpine:v3.11(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Alpine:v3.12(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Alpine:v3.13(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Alpine:v3.14(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Alpine:v3.15(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Alpine:v3.16(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Alpine:v3.17(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Alpine:v3.18(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Alpine:v3.19(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Alpine:v3.20(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Alpine:v3.21(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Alpine:v3.22(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-r0—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-1—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.51-1—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 43× in last 7d / 193× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 796 total refreshes for this CVE.

  1. 2026-10-04 12:01 UTCGHSA enrichment
  2. 2026-10-04 07:55 UTCGHSA enrichment
  3. 2026-10-04 03:49 UTCGHSA enrichment
  4. 2026-10-03 23:43 UTCGHSA enrichment
  5. 2026-10-03 19:37 UTCGHSA enrichment
  6. 2026-10-03 15:31 UTCGHSA enrichment
  7. 2026-10-03 11:25 UTCGHSA enrichment
  8. 2026-10-03 07:18 UTCGHSA enrichment
  9. 2026-10-03 03:12 UTCGHSA enrichment
  10. 2026-10-02 23:05 UTCGHSA enrichment
  11. 2026-10-02 18:57 UTCGHSA enrichment
  12. 2026-10-02 14:50 UTCGHSA enrichment
  13. 2026-10-02 10:44 UTCGHSA enrichment
  14. 2026-10-02 06:37 UTCGHSA enrichment
  15. 2026-10-02 02:29 UTCGHSA enrichment
  16. 2026-10-01 22:22 UTCGHSA enrichment
  17. 2026-10-01 18:15 UTCGHSA enrichment
  18. 2026-10-01 14:07 UTCGHSA enrichment
  19. 2026-10-01 10:01 UTCGHSA enrichment
  20. 2026-10-01 05:55 UTCGHSA enrichment
  21. 2026-10-01 01:49 UTCGHSA enrichment
  22. 2026-09-30 21:43 UTCGHSA enrichment
  23. 2026-09-30 17:37 UTCGHSA enrichment
  24. 2026-09-30 13:30 UTCGHSA enrichment
  25. 2026-09-30 09:24 UTCGHSA enrichment
Show 75 more
  1. 2026-09-30 05:15 UTCGHSA enrichment
  2. 2026-09-30 01:08 UTCGHSA enrichment
  3. 2026-09-29 21:02 UTCGHSA enrichment
  4. 2026-09-29 16:54 UTCGHSA enrichment
  5. 2026-09-29 12:48 UTCGHSA enrichment
  6. 2026-09-29 08:42 UTCGHSA enrichment
  7. 2026-09-29 04:36 UTCGHSA enrichment
  8. 2026-09-29 00:30 UTCEG score recompute
  9. 2026-09-29 00:29 UTCGHSA enrichment
  10. 2026-09-28 20:23 UTCGHSA enrichment
  11. 2026-09-28 16:17 UTCGHSA enrichment
  12. 2026-09-28 12:10 UTCGHSA enrichment
  13. 2026-09-28 08:04 UTCGHSA enrichment
  14. 2026-09-28 03:57 UTCGHSA enrichment
  15. 2026-09-27 23:51 UTCGHSA enrichment
  16. 2026-09-27 21:51 UTCCISA KEV update
  17. 2026-09-27 19:44 UTCGHSA enrichment
  18. 2026-09-27 15:37 UTCGHSA enrichment
  19. 2026-09-27 11:29 UTCGHSA enrichment
  20. 2026-09-27 07:22 UTCGHSA enrichment
  21. 2026-09-27 03:15 UTCGHSA enrichment
  22. 2026-09-26 23:08 UTCGHSA enrichment
  23. 2026-09-26 18:58 UTCGHSA enrichment
  24. 2026-09-26 14:50 UTCGHSA enrichment
  25. 2026-09-26 10:43 UTCGHSA enrichment
  26. 2026-09-26 06:34 UTCGHSA enrichment
  27. 2026-09-26 02:25 UTCGHSA enrichment
  28. 2026-09-25 22:19 UTCGHSA enrichment
  29. 2026-09-25 19:35 UTCCISA KEV update
  30. 2026-09-25 18:09 UTCGHSA enrichment
  31. 2026-09-25 14:55 UTCCISA KEV update
  32. 2026-09-25 13:59 UTCGHSA enrichment
  33. 2026-09-25 09:50 UTCGHSA enrichment
  34. 2026-09-25 05:44 UTCGHSA enrichment
  35. 2026-09-25 01:38 UTCGHSA enrichment
  36. 2026-09-24 21:31 UTCGHSA enrichment
  37. 2026-09-24 19:31 UTCCISA KEV update
  38. 2026-09-24 17:25 UTCGHSA enrichment
  39. 2026-09-24 13:19 UTCGHSA enrichment
  40. 2026-09-24 09:13 UTCGHSA enrichment
  41. 2026-09-24 05:07 UTCGHSA enrichment
  42. 2026-09-24 01:00 UTCGHSA enrichment
  43. 2026-09-23 20:54 UTCGHSA enrichment
  44. 2026-09-23 16:48 UTCGHSA enrichment
  45. 2026-09-23 12:42 UTCGHSA enrichment
  46. 2026-09-23 08:36 UTCGHSA enrichment
  47. 2026-09-23 04:30 UTCGHSA enrichment
  48. 2026-09-23 00:24 UTCGHSA enrichment
  49. 2026-09-22 20:18 UTCGHSA enrichment
  50. 2026-09-22 19:36 UTCCISA KEV update
  51. 2026-09-22 16:12 UTCGHSA enrichment
  52. 2026-09-22 12:05 UTCGHSA enrichment
  53. 2026-09-22 07:59 UTCGHSA enrichment
  54. 2026-09-22 03:53 UTCGHSA enrichment
  55. 2026-09-21 23:47 UTCGHSA enrichment
  56. 2026-09-21 19:41 UTCGHSA enrichment
  57. 2026-09-21 19:09 UTCCISA KEV update
  58. 2026-09-21 15:35 UTCGHSA enrichment
  59. 2026-09-21 11:29 UTCGHSA enrichment
  60. 2026-09-21 07:23 UTCGHSA enrichment
  61. 2026-09-21 03:17 UTCGHSA enrichment
  62. 2026-09-20 23:10 UTCGHSA enrichment
  63. 2026-09-20 19:04 UTCGHSA enrichment
  64. 2026-09-20 14:57 UTCGHSA enrichment
  65. 2026-09-20 10:51 UTCGHSA enrichment
  66. 2026-09-20 06:45 UTCGHSA enrichment
  67. 2026-09-20 02:35 UTCGHSA enrichment
  68. 2026-09-19 22:29 UTCGHSA enrichment
  69. 2026-09-19 18:23 UTCGHSA enrichment
  70. 2026-09-19 14:17 UTCGHSA enrichment
  71. 2026-09-19 10:10 UTCGHSA enrichment
  72. 2026-09-19 06:04 UTCGHSA enrichment
  73. 2026-09-19 01:58 UTCGHSA enrichment
  74. 2026-09-18 21:52 UTCGHSA enrichment
  75. 2026-09-18 19:20 UTCCISA KEV update

Publicly available exploits

(10 references)

Working exploit code is in the public domain (2 Metasploit modules) (5 GitHub PoCs) (3 Exploit-DB entries). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Exploit-DBEDB-50512✓ verified
    First seen Nov 11, 2021

    Apache HTTP Server 2.4.50 - Remote Code Execution (RCE) (3)

    Open source ↗
  • Exploit-DBEDB-50406✓ verified
    First seen Oct 13, 2021

    Apache HTTP Server 2.4.50 - Path Traversal & Remote Code Execution (RCE)

    Open source ↗
  • Metasploitauxiliary/scanner/http/apache_normalize_path✓ verified
    First seen May 10, 2021

    Apache 2.4.49/2.4.50 Traversal RCE scanner

    Open source ↗
  • Metasploitexploit/multi/http/apache_normalize_path_rce✓ verified
    First seen May 10, 2021

    Apache 2.4.49/2.4.50 Traversal RCE

    Open source ↗
  • GitHub PoCBassoNicolas/CVE-2021-42013
    First seen Apr 7, 2024

    CVE-2021-42013 Vulnerability Scanner This Python script checks for the Remote Code Execution (RCE) vulnerability (CVE-2021-42013) in Apache 2.4.50.

    Open source ↗
  • GitHub PoCK3ysTr0K3R/CVE-2021-42013-EXPLOIT
    First seen Aug 25, 2023

    A PoC exploit for CVE-2021-42013 - Apache 2.4.49 & 2.4.50 Remote Code Execution

    Open source ↗
  • GitHub PoCasaotomo/CVE-2021-42013-Apache-RCE-Poc-Exp
    First seen Dec 23, 2021

    Apache 远程代码执行 （CVE-2021-42013）批量检测工具：Apache HTTP Server是美国阿帕奇（Apache）基金会的一款开源网页服务器。该服务器具有快速、可靠且可通过简单的API进行扩充的特点，发现 Apache HTTP Server 2.4.50 中针对 CVE-2021-41773 的修复不够充分。攻击者可以使用路径遍历攻击将 URL 映射到由类似别名的指令配置的目录之外的文件。如果这些目录之外的文件不受通常的默认配置“要求全部拒绝”的保护，则这些请求可能会成功。如果还为这些别名路径启用了 CGI 脚本，则这可能允许远程代码执行。此问题仅影响 Apache 2.4.49 和 Apache 2.4.50，而不影响更早版本。

    Open source ↗
  • GitHub PoCwalnutsecurity/cve-2021-42013
    First seen Oct 27, 2021

    cve-2021-42013.py is a python script that will help in finding Path Traversal or Remote Code Execution vulnerability in Apache 2.4.50

    Open source ↗
  • Exploit-DBEDB-50446
    First seen Oct 25, 2021

    Apache HTTP Server 2.4.50 - Remote Code Execution (RCE) (2)

    Open source ↗
  • GitHub PoCTheLastVvV/CVE-2021-42013_Reverse-Shell
    First seen Oct 24, 2021

    PoC CVE-2021-42013 reverse shell Apache 2.4.50 with CGI

    Open source ↗

Related CVEs(same product + same CWE)

Frequently asked(6)

What is CVE-2021-42013?
CVE-2021-42013 is a critical vulnerability published on October 7, 2021. It was found that the fix for CVE-2021-41773 in Apache HTTP Server 2.4.50 was insufficient. 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…
When was CVE-2021-42013 disclosed?
CVE-2021-42013 was first published on October 7, 2021, with the most recent update on October 27, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-42013 actively exploited?
Yes. CISA added CVE-2021-42013 to the Known Exploited Vulnerabilities catalog on November 3, 2021, affecting Apache HTTP Server. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate attention. No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation, and watch the vendor's advisory for the fix.
What is the CVSS score of CVE-2021-42013?
CVE-2021-42013 has a CVSS v3 base score of 9.8 (NVD).
Which products are affected by CVE-2021-42013?
CVE-2021-42013 affects Apache HTTP Server. The affected packages EchelonGraph has on record, with version ranges, are listed in the Affected Packages section of this page.
How do I remediate CVE-2021-42013?
No fix for CVE-2021-42013 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix.

Dependency Blast Radius

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