Vulnerability record

CVE-2021-40438

A permanent, source-backed tracker page. Values are shown only when returned; explicit gaps and read failures remain different states.

Full record read. Reported values and explicit gaps below come from the tracked record. Tracker snapshot: Aug 9, 2026.

What it is

Reported

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. Source description excerpt; complete tracked detail loads below.

NVD published: Sep 16, 2021 · Source record updated: Aug 9, 2026 · Tracker snapshot: Aug 9, 2026

What is affected

Reported

Apache — Apache. Product-level identification only; no affected-version conclusion is available from this field.

NVD published: Sep 16, 2021 · Source record updated: Aug 9, 2026 · Tracker snapshot: Aug 9, 2026

Urgency and basis

Reported

Act now · 572.9

Tracker decision tier from the evidence detailed below · Source record updated: Aug 9, 2026 · Tracker snapshot: Aug 9, 2026

Exploitation evidence

Reported

Active exploitation · CISA KEV · VulnCheck KEV · ENISA exploited-vulnerability catalog

Active since: Dec 1, 2021 · CISA KEV added: Dec 1, 2021 · VulnCheck KEV added: Dec 1, 2021 · ENISA added: Dec 1, 2021 · Source record updated: Aug 9, 2026 · Tracker snapshot: Aug 9, 2026

What to do

Reported

Apply updates per vendor instructions.

Source remediation ↗

Tracked source remediation field · Source record updated: Aug 9, 2026 · Tracker snapshot: Aug 9, 2026

Evidence detail

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