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Weekly Signal
Live intelligence Updated 19 Aug 2026 · 20:27 UTC

Apache, Broadcom, Debian +8 more · Apache, Http Server, Brocade Fabric Operating System Firmware +36 more

CVE-2021-40438

Apache HTTP Server-Side Request Forgery (SSRF)

Recommended action

Treat this as an immediate remediation priority. Apply updates per vendor instructions.

View response plan
CVSS9.0
EPSS100.0%
KEVYes
ExploitationConfirmed exploitation
PatchPatch or guidance available ↓

Assessment

Why it matters

CISA lists this vulnerability as known to be exploited; exploitation is confirmed; EPSS is 100.0%; technical severity is CVSS 9.0.

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.

Who should care

  • Teams operating Apache, Http Server, Brocade Fabric Operating System Firmware +36 more
  • Vulnerability and exposure management teams
  • Security operations teams monitoring exploitation activity

Response plan

What I would do

  1. Confirm whether Apache, Http Server, Brocade Fabric Operating System Firmware +36 more is present in the environment.
  2. Identify affected versions and establish whether vulnerable services are exposed or reachable.
  3. Apply updates per vendor instructions.
  4. Review relevant security telemetry for evidence of attempted or successful exploitation.
  5. Document the remediation decision and track it to verified completion.

Vendor remediation

Patch and remediation links

Use the vendor source below to confirm the correct fixed version, package or mitigation for your affected product.

Technical details

CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
CWE
CWE-918
Affected versions
Apache Apache; Apache Http Server (End Including: 2.4.48); Broadcom Brocade Fabric Operating System Firmware (Version: -); Debian Debian Linux (Version: 11.0); F5 F5os (Start Including: 1.2.0, End Including: 1.2.1); Fedoraproject Fedora (Version: 35); Netapp Cloud Backup (Version: -); Netapp Clustered Data Ontap (Version: -)
Published
16 September 2021
Attack vector
Network
Privileges required
None
User interaction
None

Signal timeline

  1. CVE published
  2. Added to CISA KEV
  3. Latest EPSS score: 100.0%
  4. Signal calculated at 87

External references

Live public intelligence This assessment combines public-source evidence. Validate the affected product, version and exposure against your own environment before making a risk decision.