CVE-2026-18174

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 91% 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
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.3Exploit: None knownExposed: 0

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

@fastify/forwarded resolves client addresses from the X-Forwarded-For header. In versions before 3.0.2, when the header contains two or more comma separated entries, the parser trims only space characters and does not strip horizontal tabs, even though RFC 7230 defines optional whitespace as both space and tab. As a result, an entry padded with a tab keeps the literal tab in the resolved address string. Applications that make exact string match security decisions on the resolved client IP, such as an allowlist, a blocklist, a per IP rate limit key, or audit log correlation, can be evaded because the tab corrupted string no longer matches the expected value. This does not cross the trust boundary, since a tab corrupted string is not a valid IP and cannot be mistaken for a trusted proxy. The issue is fixed in @fastify/forwarded 3.0.2.

CVSS v3
5.3
EG Score
5.3(medium)
EG Risk
39(Track)
EG Risk 39/100SSVC: 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
Severity53% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
9%
KEV
Not listed

Published

July 29, 2026

Last Modified

August 5, 2026

Advisory Details (2)

Auto-updated Jul 29, 2026
Patch available. Sources: github.
generic

Security Advisories | OpenJS Foundation CVE Numbering Authority

https://cna.openjsf.org/security-advisories.html
github Patch Available

@fastify/forwarded vulnerable to improper input validation via unstripped tab characters in X-Forwarded-For · Advisory · fastify/forwarded · GitHub

https://github.com/fastify/forwarded/security/advisories/GHSA-2849-m2w7-xm8f

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 9× 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.

  1. 2026-08-26 14:46 UTCEPSS rescore
  2. 2026-08-26 08:09 UTCEG score recompute
  3. 2026-08-25 13:48 UTCEPSS rescore
  4. 2026-08-25 06:11 UTCEG score recompute
  5. 2026-08-22 00:23 UTCEG score recompute
  6. 2026-08-21 23:49 UTCEPSS rescore
  7. 2026-08-20 22:55 UTCEPSS rescore
  8. 2026-08-19 20:32 UTCEG score recompute
  9. 2026-08-19 17:03 UTCEPSS rescore
  10. 2026-08-18 18:36 UTCEG score recompute
  11. 2026-08-18 13:48 UTCEPSS rescore
  12. 2026-08-17 13:47 UTCEPSS rescore
  13. 2026-08-17 12:56 UTCEG score recompute
  14. 2026-08-16 14:56 UTCEPSS rescore
  15. 2026-08-16 11:01 UTCEG score recompute
  16. 2026-08-16 02:14 UTCEPSS rescore
  17. 2026-08-15 09:06 UTCEG score recompute
  18. 2026-08-15 01:30 UTCEPSS rescore
  19. 2026-08-14 07:10 UTCEG score recompute
  20. 2026-08-13 22:00 UTCEPSS rescore
  21. 2026-08-13 05:14 UTCEG score recompute
  22. 2026-08-12 13:50 UTCEPSS rescore
  23. 2026-08-12 03:19 UTCEG score recompute
  24. 2026-08-11 13:42 UTCEPSS rescore
  25. 2026-08-11 01:23 UTCEG score recompute
Show 23 more
  1. 2026-08-11 00:00 UTCEPSS rescore
  2. 2026-08-09 23:28 UTCEG score recompute
  3. 2026-08-09 13:46 UTCEPSS rescore
  4. 2026-08-08 21:33 UTCEG score recompute
  5. 2026-08-08 16:37 UTCEPSS rescore
  6. 2026-08-07 19:38 UTCEG score recompute
  7. 2026-08-06 17:42 UTCEG score recompute
  8. 2026-08-06 13:46 UTCEPSS rescore
  9. 2026-08-05 19:17 UTCEPSS rescore
  10. 2026-08-05 02:36 UTCEG score recompute
  11. 2026-08-04 15:10 UTCEPSS rescore
  12. 2026-08-04 00:41 UTCEG score recompute
  13. 2026-08-03 10:35 UTCEPSS rescore
  14. 2026-08-02 22:46 UTCEG score recompute
  15. 2026-08-02 02:26 UTCEPSS rescore
  16. 2026-08-01 20:50 UTCEG score recompute
  17. 2026-08-01 04:15 UTCEPSS rescore
  18. 2026-07-30 16:58 UTCEG score recompute
  19. 2026-07-29 16:25 UTCEG score recompute
  20. 2026-07-29 15:33 UTCEG score recompute
  21. 2026-07-29 14:19 UTCEG score recompute
  22. 2026-07-29 13:58 UTCEG score recompute
  23. 2026-07-29 13:57 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-18174?
CVE-2026-18174 is a medium vulnerability published on July 29, 2026. @fastify/forwarded resolves client addresses from the X-Forwarded-For header. In versions before 3.0.2, when the header contains two or more comma separated entries, the parser trims only space characters and does not strip horizontal tabs, even though RFC 7230 defines optional whitespace as both…
When was CVE-2026-18174 disclosed?
CVE-2026-18174 was first published in the National Vulnerability Database on July 29, 2026, with the most recent update on August 5, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-18174 actively exploited?
CVE-2026-18174 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 91.0% of all scored CVEs.
What is the CVSS score of CVE-2026-18174?
CVE-2026-18174 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-18174?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-18174, 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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