CVE-2021-40438: Used in ransomware campaigns — CISA KEV
A crafted request uri-path can cause mod_proxy to forward the request to an origin server choosen by the remote user. This issue affects Apache HTTP Server 2.4.48 and earlier.
CISA KEV — Actively Exploited
A crafted request uri-path can cause mod_proxy to forward the request to an origin server choosen by the remote user
Vendor / Product
— / Apache / Apache
CVSS / EPSS
9.0 CRITICAL · EPSS 100.00%
01What CISA says about this vulnerability
A crafted request uri-path can cause mod_proxy to forward the request to an origin server choosen by the remote user. This issue affects Apache HTTP Server 2.4.48 and earlier.
02Required action — verbatim from CISA
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
03Notes & references
- cert-portal.siemens.com — https://cert-portal.siemens.com/productcert/pdf/ssa-685781.pdf
- httpd.apache.org — https://httpd.apache.org/security/vulnerabilities_24.html
- lists.apache.org — https://lists.apache.org/thread.html/r210807d0bb55f4aa6fbe1512be6bcc4dacd64e8494…
- lists.apache.org — https://lists.apache.org/thread.html/r2eb200ac1340f69aa22af61ab34780c531d1104379…
- lists.apache.org — https://lists.apache.org/thread.html/r3925e167d5eb1c75def3750c155d753064e1d34a14…
- lists.apache.org — https://lists.apache.org/thread.html/r61fdbfc26ab170f4e6492ef3bd5197c20b862ce156…
- lists.apache.org — https://lists.apache.org/thread.html/r82838efc5fa6fc4c73986399c9b71573589f78b318…
- lists.apache.org — https://lists.apache.org/thread.html/r82c077663f9759c7df5a6656f925b3ee4f55fcd33c…
- lists.apache.org — https://lists.apache.org/thread.html/rf6954e60b1c8e480678ce3d02f61b8a78899778565…
- lists.debian.org — https://lists.debian.org/debian-lts-announce/2021/10/msg00001.html
04SARA's analyst layer — why this matters
This vulnerability is currently on the CISA KEV list, which CISA only adds CVEs to when there is reliable evidence of active exploitation in the wild. For federal civilian agencies, BOD 22-01 requires remediation by the due date above. For everyone else, KEV is the strongest "patch immediately" signal you can get from public threat intel.
05Affected products (summary)
No structured affected-product list available — see references below for vendor advisories.
06Detection
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