CVE-2026-18427

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5%, top 62% 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, secondary
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.5Exploit: None knownExposed: 0

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

@fastify/static before version 10.1.3 contains an incomplete fix for a previous route guard bypass. The static file handler rejected only parent directory segments, but it did not canonicalize dot segments, duplicate slashes, encoded dots, or backslashes before route matching and before delegating to the send layer. As a result, an unauthenticated attacker could request a file protected by a route based guard using a non canonical path form that misses the guarded route yet resolves back onto the protected file, disclosing its contents. Applications that protect a subtree of the static root with a route based guard are affected, while applications relying on the allowedPath option are not. This is fixed in @fastify/static 10.1.3, which canonicalizes the pathname, including rejecting backslashes, on the path used for routing and serving.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
38(Track)
EG Risk 38/100SSVC: 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
Severity75% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
38%
KEV
Not listed

Published

August 6, 2026

Last Modified

August 6, 2026

Advisory Details (2)

Auto-updated Aug 6, 2026
Patch available. Sources: github.
github Patch Available

@fastify/static vulnerable to route guard bypass via non-canonical path segments · Advisory · fastify/fastify-static · GitHub

https://github.com/fastify/fastify-static/security/advisories/GHSA-423g-23ch-w7c6
generic

Security Advisories | OpenJS Foundation CVE Numbering Authority

https://cna.openjsf.org/security-advisories.html

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 37× 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. 2026-08-25 17:47 UTCEG score recompute
  2. 2026-08-25 13:48 UTCEPSS rescore
  3. 2026-08-24 19:47 UTCEG score recompute
  4. 2026-08-23 10:48 UTCEG score recompute
  5. 2026-08-23 00:19 UTCEPSS rescore
  6. 2026-08-22 01:49 UTCEG score recompute
  7. 2026-08-21 23:49 UTCEPSS rescore
  8. 2026-08-21 03:49 UTCEG score recompute
  9. 2026-08-20 22:55 UTCEPSS rescore
  10. 2026-08-19 18:50 UTCEG score recompute
  11. 2026-08-19 17:03 UTCEPSS rescore
  12. 2026-08-18 20:20 UTCEG score recompute
  13. 2026-08-18 13:48 UTCEPSS rescore
  14. 2026-08-17 22:21 UTCEG score recompute
  15. 2026-08-17 13:47 UTCEPSS rescore
  16. 2026-08-17 00:21 UTCEG score recompute
  17. 2026-08-16 14:56 UTCEPSS rescore
  18. 2026-08-16 02:21 UTCEG score recompute
  19. 2026-08-16 02:14 UTCEPSS rescore
  20. 2026-08-15 04:22 UTCEG score recompute
  21. 2026-08-15 01:30 UTCEPSS rescore
  22. 2026-08-14 06:20 UTCEG score recompute
  23. 2026-08-13 22:00 UTCEPSS rescore
  24. 2026-08-12 21:20 UTCEG score recompute
  25. 2026-08-12 13:50 UTCEPSS rescore
Show 12 more
  1. 2026-08-11 23:19 UTCEG score recompute
  2. 2026-08-11 13:42 UTCEPSS rescore
  3. 2026-08-11 01:19 UTCEG score recompute
  4. 2026-08-11 00:00 UTCEPSS rescore
  5. 2026-08-09 16:20 UTCEG score recompute
  6. 2026-08-09 13:46 UTCEPSS rescore
  7. 2026-08-08 18:22 UTCEG score recompute
  8. 2026-08-08 16:37 UTCEPSS rescore
  9. 2026-08-07 20:22 UTCEG score recompute
  10. 2026-08-06 16:32 UTCEG score recompute
  11. 2026-08-06 15:31 UTCEG score recompute
  12. 2026-08-06 15:31 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-18427?
CVE-2026-18427 is a high vulnerability published on August 6, 2026. @fastify/static before version 10.1.3 contains an incomplete fix for a previous route guard bypass. The static file handler rejected only parent directory segments, but it did not canonicalize dot segments, duplicate slashes, encoded dots, or backslashes before route matching and before delegating…
When was CVE-2026-18427 disclosed?
CVE-2026-18427 was first published in the National Vulnerability Database on August 6, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-18427 actively exploited?
CVE-2026-18427 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 62.2% of all scored CVEs.
What is the CVSS score of CVE-2026-18427?
CVE-2026-18427 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-18427?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-18427, 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

Explore the affected products and dependency analysis for CVE-2026-18427

Explore →

Is Your Infrastructure Affected by CVE-2026-18427?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs