CVE-2021-21322

CRITICALNVD 10.010.0—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 10.0 under NVD CVSS v3. EPSS exploit probability: 1.9%, top 22% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 3 sources updated this week
10.0
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 2%CVSS: 10.0Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

fastify-http-proxy is an npm package which is a fastify plugin for proxying your http requests to another server, with hooks. By crafting a specific URL, it is possible to escape the prefix of the proxied backend service. If the base url of the proxied server is /pub/, a user expect that accessing /priv on the target service would not be possible. In affected versions, it is possible. This is fixed in version 4.3.1.

CVSS v3
10.0
EG Score
10.0(medium)
EG Risk
—
EPSS
77.8%
KEV
Not listed

Published

March 2, 2021

Last Modified

November 21, 2024

Advisory Details (2)

Auto-updated Jul 18, 2026
Patch available. Sources: github_commit, github.
github Patch Available

Prefix escape · Advisory · fastify/fastify-http-proxy · GitHub

https://github.com/fastify/fastify-http-proxy/security/advisories/GHSA-c4qr-gmr9-v23w
github_commit Patch Available

commit 02d9b43c770a (fastify/fastify-http-proxy)

Patch available: fastify/fastify-http-proxy v8.2.0 (contains commit 02d9b43c770a)

https://github.com/fastify/fastify-http-proxy/commit/02d9b43c770aa16bc44470edecfaeb7c17985016

Vendor Advisories for CVE-2021-21322(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
fastify-http-proxy—4.3.1—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 10× in last 7d / 48× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 101 total refreshes for this CVE.

  1. 2026-07-22 22:43 UTCEG score recompute
  2. 2026-07-22 14:05 UTCEPSS rescore
  3. 2026-07-21 15:22 UTCEPSS rescore
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Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2021-21322?
CVE-2021-21322 is a critical vulnerability published on March 2, 2021. fastify-http-proxy is an npm package which is a fastify plugin for proxying your http requests to another server, with hooks. By crafting a specific URL, it is possible to escape the prefix of the proxied backend service. If the base url of the proxied server is /pub/, a user expect that accessing…
When was CVE-2021-21322 disclosed?
CVE-2021-21322 was first published in the National Vulnerability Database on March 2, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-21322 actively exploited?
CVE-2021-21322 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 77.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-21322?
CVE-2021-21322 has a CVSS v3 base score of 10.0 (NVD).
How do I remediate CVE-2021-21322?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-21322, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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