CVE-2026-16732

MEDIUMPre-NVD 6.16.1—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2% (4th percentile of EPSS-scored CVEs). 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, secondary
6.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 6.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

fastify is a fast and low overhead web framework for Node.js. Impact: the fix for CVE-2026-3635 added a guard on the forwarded-header reads used to derive the request host, protocol, hostname, ip, and ips values, checking the connecting address. That guard closes the IP, CIDR, and custom-function forms of trustProxy correctly, because those forms compile to predicates that inspect the connecting address. The hop-count form, where trustProxy is set to a number, compiles to a predicate that structurally ignores the address, so the guard is always satisfied for any hop count of one or more. Applications configured with a numeric trustProxy value, such as trustProxy set to 1 for a single reverse proxy, remain vulnerable: an attacker who can reach the Fastify origin directly, bypassing the front-facing proxy, can spoof the forwarded request fields exactly as in the unpatched version. The impact class matches the parent CVE-2026-3635, including host injection in generated URLs, HTTPS-enforcement bypass, secure-cookie and CSRF-origin bypass, and host-based routing and cache poisoning. Affected versions are fastify from 5.8.3 up to but not including 5.12.1. Patches: patched in fastify 5.12.1, where the numeric form of trustProxy is disabled at runtime and removed from the TypeScript type union. Workarounds: migrate to an IP, CIDR, or custom-function trustProxy value that validates the connecting address, and ensure the Fastify origin is only reachable through the trusted proxy chain.

CVSS v3
6.1
EG Score
6.1MEDIUMmedium confidence
EG Risk
28
EG Risk 28/100CISA SSVC

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
Severity61% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.2%
EPSS %ILE
4th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 18, 2026

Last Modified

September 2, 2026

Advisory Details (2)

Auto-updated Aug 18, 2026
Patch available. Sources: github.
generic

Security Advisories | OpenJS Foundation CVE Numbering Authority

https://cna.openjsf.org/security-advisories.html
githubMentions a patch (unverified)

fastify vulnerable to X-Forwarded-* spoofing under trustProxy hop-count · Advisory · fastify/fastify · GitHub

https://github.com/fastify/fastify/security/advisories/GHSA-3m5p-2c4r-xxw2

Vendor Advisories for CVE-2026-16732(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 rangeFix by version rangeDependents
fastify—
  • 5.8.3 up to 5.12.1: fixed in 5.12.1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 40× 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.

  1. 2026-10-09 20:06 UTCEPSS rescore
  2. 2026-10-07 23:47 UTCEPSS rescore
  3. 2026-10-07 11:10 UTCEG score recompute
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  25. 2026-09-19 16:07 UTCEG score recompute
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  1. 2026-09-18 19:27 UTCEPSS rescore
  2. 2026-09-18 14:52 UTCEG score recompute
  3. 2026-09-17 13:43 UTCEG score recompute
  4. 2026-09-16 14:07 UTCEPSS rescore
  5. 2026-09-16 12:33 UTCEG score recompute
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  9. 2026-09-13 16:46 UTCEPSS rescore
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  20. 2026-09-07 16:01 UTCEPSS rescore
  21. 2026-09-06 19:43 UTCEG score recompute
  22. 2026-09-06 13:47 UTCEPSS rescore
  23. 2026-09-05 18:26 UTCEG score recompute
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  25. 2026-09-04 05:06 UTCEPSS rescore
  26. 2026-09-02 14:46 UTCEG score recompute
  27. 2026-09-02 14:11 UTCEPSS rescore
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  29. 2026-09-01 13:53 UTCEPSS rescore
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  32. 2026-08-30 19:17 UTCEPSS rescore
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  34. 2026-08-29 21:08 UTCEG score recompute
  35. 2026-08-28 21:41 UTCEPSS rescore
  36. 2026-08-28 00:03 UTCEG score recompute
  37. 2026-08-27 14:25 UTCEPSS rescore
  38. 2026-08-26 22:53 UTCEG score recompute
  39. 2026-08-26 14:46 UTCEPSS rescore
  40. 2026-08-25 21:43 UTCEG score recompute
  41. 2026-08-25 13:48 UTCEPSS rescore
  42. 2026-08-24 20:13 UTCEG score recompute
  43. 2026-08-23 19:04 UTCEG score recompute
  44. 2026-08-23 00:19 UTCEPSS rescore
  45. 2026-08-22 17:55 UTCEG score recompute
  46. 2026-08-21 23:49 UTCEPSS rescore
  47. 2026-08-21 16:46 UTCEG score recompute
  48. 2026-08-20 22:55 UTCEPSS rescore
  49. 2026-08-20 15:36 UTCEG score recompute
  50. 2026-08-19 17:03 UTCEPSS rescore
  51. 2026-08-19 14:27 UTCEG score recompute
  52. 2026-08-19 13:40 UTCEG score recompute
  53. 2026-08-18 21:36 UTCEG score recompute
  54. 2026-08-18 20:33 UTCEG score recompute
  55. 2026-08-18 20:33 UTCMITRE cvelistV5first tracked

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-16732?
CVE-2026-16732 is a medium vulnerability published on August 18, 2026. fastify is a fast and low overhead web framework for Node.js. Impact: the fix for CVE-2026-3635 added a guard on the forwarded-header reads used to derive the request host, protocol, hostname, ip, and ips values, checking the connecting address. That guard closes the IP, CIDR, and custom-function…
When was CVE-2026-16732 disclosed?
CVE-2026-16732 was first published on August 18, 2026, with the most recent update on September 2, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-16732 actively exploited?
CVE-2026-16732 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (4th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-16732?
CVE-2026-16732 has a CVSS base score of 6.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-16732?
A fix for CVE-2026-16732 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-16732 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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