PatchSiren

PatchSiren cyber security CVE debrief

CVE-2021-42013 Apache CVE debrief

CVE-2021-42013 is a path traversal vulnerability in Apache HTTP Server that was added to CISA’s Known Exploited Vulnerabilities catalog on 2021-11-03. CISA lists it as known to be exploited and associated with known ransomware campaign use, so exposed Apache HTTP Server deployments should be treated as a high-priority remediation item.

Vendor
Apache
Product
HTTP Server
CVSS
Unknown
CISA KEV
Listed
Original CVE published
2021-11-03
Original CVE updated
2021-11-03
Advisory published
2021-11-03
Advisory updated
2021-11-03

Who should care

Organizations running Apache HTTP Server, especially internet-facing instances, should prioritize this CVE. Security and operations teams responsible for patch management, web hosting, reverse proxy/front-end infrastructure, and incident response should review exposure and confirm remediation status.

Technical summary

The available source corpus identifies CVE-2021-42013 as a path traversal issue in Apache HTTP Server. CISA’s KEV entry confirms known exploitation and states that affected systems should be updated per vendor instructions. No further technical details are provided in the supplied sources.

Defensive priority

High. This vulnerability is in CISA’s Known Exploited Vulnerabilities catalog and has known ransomware campaign use, which makes timely remediation especially important for exposed systems.

Recommended defensive actions

  • Identify all Apache HTTP Server deployments and confirm whether they are exposed to untrusted network access.
  • Apply vendor-recommended updates as soon as possible.
  • Validate that patching has been completed across production, staging, and any externally reachable instances.
  • Review logs and security telemetry for signs of suspicious access to Apache HTTP Server endpoints.
  • If remediation is delayed, apply compensating controls to reduce exposure until updates are installed.

Evidence notes

This debrief is based only on the supplied CVE metadata and official links. The strongest evidence comes from CISA’s Known Exploited Vulnerabilities catalog, which marks CVE-2021-42013 as actively exploited and notes known ransomware campaign use. The supplied corpus does not include a vendor advisory or CVSS score.

Sources and references

Verified primary and authoritative sources

  • CVE-2021-42013 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2021-42013

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2021-42013 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2021-42013

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

  • CISA Known Exploited Vulnerabilities catalog

    Publisher, destination, and source semantics verified

    URL: https://www.cisa.gov/known-exploited-vulnerabilities-catalog

    Cybersecurity and Infrastructure Security Agency - Official CISA catalog of vulnerabilities known to be exploited in the wild.

Supplemental references

  • Source item URL

    Unverified legacy reference

    URL: https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

    cisa_kev

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.