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
10.0EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 2%CVSS: 10.0Exploit: None knownExposed: 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
50(Track)
EG Risk 50/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity100% × 45%
Exploitation2% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
2%
EPSS %ILE
74%
KEV
Not listed

Published

March 2, 2021

Last Modified

November 21, 2024

Advisory Details (2)

Auto-updated Aug 22, 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 v8.2.1 (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 6× in last 7d / 28× 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 134 total refreshes for this CVE.

  1. 2026-08-25 13:45 UTCEPSS rescore
  2. 2026-08-23 00:16 UTCEPSS rescore
  3. 2026-08-21 23:46 UTCEPSS rescore
  4. 2026-08-20 22:52 UTCEPSS rescore
  5. 2026-08-20 07:55 UTCOSV refresh
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  20. 2026-08-05 03:10 UTCOSV refresh
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  1. 2026-07-30 16:25 UTCEPSS rescore
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  8. 2026-07-23 01:57 UTCEG score recompute
  9. 2026-07-22 22:43 UTCEG score recompute
  10. 2026-07-22 14:05 UTCEPSS rescore
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  16. 2026-07-19 00:59 UTCOSV refresh
  17. 2026-07-18 10:02 UTCEPSS rescore
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  19. 2026-07-15 16:55 UTCEPSS rescore
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  28. 2026-07-11 08:25 UTCEPSS rescore
  29. 2026-07-09 19:07 UTCEPSS rescore
  30. 2026-07-08 15:12 UTCEPSS rescore
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  40. 2026-07-01 15:03 UTCEPSS rescore
  41. 2026-07-01 07:48 UTCOSV refresh
  42. 2026-06-30 23:20 UTCEPSS rescore
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  44. 2026-06-29 14:04 UTCEPSS rescore
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  49. 2026-06-27 03:06 UTCEPSS rescore
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  51. 2026-06-25 13:48 UTCEPSS rescore
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  55. 2026-06-23 21:31 UTCEPSS rescore
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  65. 2026-06-18 17:51 UTCEPSS rescore
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  68. 2026-06-16 17:50 UTCEPSS rescore
  69. 2026-06-15 17:46 UTCEPSS rescore
  70. 2026-06-14 23:15 UTCEPSS rescore
  71. 2026-06-13 22:58 UTCEPSS rescore
  72. 2026-06-13 12:43 UTCOSV refresh
  73. 2026-06-12 23:10 UTCEPSS rescore
  74. 2026-06-12 23:10 UTCEPSS rescore
  75. 2026-06-11 13:58 UTCEPSS rescore

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 2% probability of exploitation in the next 30 days, which ranks it in the top 25.9% of all scored CVEs.
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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