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 11× in last 7d / 43× 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. 2026-09-19 04:55 UTCEG score recompute
  2. 2026-09-18 19:27 UTCEPSS rescore
  3. 2026-09-18 01:42 UTCEG score recompute
  4. 2026-09-16 14:07 UTCEPSS rescore
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  1. 2026-09-02 14:11 UTCEPSS rescore
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  3. 2026-09-01 13:53 UTCEPSS rescore
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  6. 2026-08-30 19:17 UTCEPSS rescore
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  8. 2026-08-29 23:20 UTCEG score recompute
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  22. 2026-08-18 13:48 UTCEPSS rescore
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  24. 2026-08-17 12:56 UTCEG score recompute
  25. 2026-08-16 14:56 UTCEPSS rescore
  26. 2026-08-16 11:01 UTCEG score recompute
  27. 2026-08-16 02:14 UTCEPSS rescore
  28. 2026-08-15 09:06 UTCEG score recompute
  29. 2026-08-15 01:30 UTCEPSS rescore
  30. 2026-08-14 07:10 UTCEG score recompute
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  35. 2026-08-11 13:42 UTCEPSS rescore
  36. 2026-08-11 01:23 UTCEG score recompute
  37. 2026-08-11 00:00 UTCEPSS rescore
  38. 2026-08-09 23:28 UTCEG score recompute
  39. 2026-08-09 13:46 UTCEPSS rescore
  40. 2026-08-08 21:33 UTCEG score recompute
  41. 2026-08-08 16:37 UTCEPSS rescore
  42. 2026-08-07 19:38 UTCEG score recompute
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  44. 2026-08-06 13:46 UTCEPSS rescore
  45. 2026-08-05 19:17 UTCEPSS rescore
  46. 2026-08-05 02:36 UTCEG score recompute
  47. 2026-08-04 15:10 UTCEPSS rescore
  48. 2026-08-04 00:41 UTCEG score recompute
  49. 2026-08-03 10:35 UTCEPSS rescore
  50. 2026-08-02 22:46 UTCEG score recompute
  51. 2026-08-02 02:26 UTCEPSS rescore
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  53. 2026-08-01 04:15 UTCEPSS rescore
  54. 2026-07-30 16:58 UTCEG score recompute
  55. 2026-07-29 16:25 UTCEG score recompute
  56. 2026-07-29 15:33 UTCEG score recompute
  57. 2026-07-29 14:19 UTCEG score recompute
  58. 2026-07-29 13:58 UTCEG score recompute
  59. 2026-07-29 13:57 UTCMITRE cvelistV5first tracked

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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 90.7% 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.

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