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CVE record · CVE-2021-40438

mod_proxy SSRF

CVSS 9.0 CriticalCriticalIn CISA KEV · ransomwareEPSS 1.00 · 99th percentile

Critical, because:

  • In CISA’s KEV catalogue since 1 Dec 2021: it is known to be exploited.
  • CVSS score 9.0: 9.0 or more.
  • CVSS score 9.0 (7.0 or more) and EPSS 1.00 (0.1 or more): a high score and a real chance of exploitation in the next 30 days.

How we decide what’s critical

Published by the CVE Program (CNA: apache) at 16 Sept 2021, 14:40 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
VendorProductVersions
Apache Software Foundation Apache HTTP Server
  • affected Apache HTTP Server 2.4 to 2.4.48, inclusive custom
Identifiers
CVE-2021-40438
CNA
apache
Weakness (CWE)
CWE-918
Tags
Published
16 Sept 2021
Updated
6 Aug 2026

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

ScoreRatingCVSSVectorSource
9.0 Critical 3.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H ADP (CISA-ADP)
  • CISA KEV Listed since 1 Dec 2021: known to be exploited. CISA reports use in ransomware campaigns.
  • EPSS 1.00, the 99th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

This record came from the full history of the CVE Program, published 16 Sept 2021. New records show when each source confirmed them.

Sources

References from the CNA

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.