CVE-2026-27959

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: 0.3%, top 74% 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
Elevated
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 7.5Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

Koa is middleware for Node.js using ES2017 async functions. Prior to versions 3.1.2 and 2.16.4, Koa's ctx.hostname API performs naive parsing of the HTTP Host header, extracting everything before the first colon without validating the input conforms to RFC 3986 hostname syntax. When a malformed Host header containing a @ symbol is received, ctx.hostname returns evil[.]com - an attacker-controlled value. Applications using ctx.hostname for URL generation, password reset links, email verification URLs, or routing decisions are vulnerable to Host header injection attacks. Versions 3.1.2 and 2.16.4 fix the issue.

CVSS v3
7.5
EG Score
7.5HIGHmedium confidence
EG Risk
65
EG Risk 65/100

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%
Exploitation40% × 40%
Automatability100% × 15%
EPSS PROB
0.5%
EPSS %ILE
42nd
KEV
Not listed

Published

February 26, 2026

Last Modified

July 15, 2026

Advisory Details (3)

Auto-updated Jun 16, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github.
github Patch Available🟡 PoC Available

Host Header Injection via `ctx.hostname` · Advisory · koajs/koa · GitHub

https://github.com/koajs/koa/security/advisories/GHSA-7gcc-r8m5-44qm
github_commit Patch Available

commit b76ddc01fdb7 (koajs/koa)

Patch available: koajs/koa v2.16.4 (contains commit b76ddc01fdb7)

https://github.com/koajs/koa/commit/b76ddc01fdb703e51652b0fd131d16394cadcfeb
github_commit Patch Available

commit 55ab9bab044e (koajs/koa)

Patch available: koajs/koa v3.1.2 (contains commit 55ab9bab044e)

https://github.com/koajs/koa/commit/55ab9bab044ead4e82c70a30a4f9dc0fc9c1b6df

Vendor Advisories for CVE-2026-27959(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(2)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatrhoai/odh-mod-arch-model-registry-rhel9:17767421412026-04-23redhat
redhatopenshift4/ose-monitoring-plugin-rhel9:17755771922026-04-16redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFix by version rangeDependents
koa—
  • 3.0.0 up to 3.1.2: fixed in 3.1.2
  • every version up to 2.16.4: fixed in 2.16.4
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 5× in last 7d / 23× 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 150 total refreshes for this CVE.

  1. 2026-10-05 17:42 UTCEPSS rescore
  2. 2026-10-04 23:21 UTCEPSS rescore
  3. 2026-10-03 14:25 UTCEPSS rescore
  4. 2026-10-01 19:49 UTCEPSS rescore
  5. 2026-09-30 15:03 UTCEPSS rescore
  6. 2026-09-28 13:51 UTCEPSS rescore
  7. 2026-09-26 15:58 UTCEPSS rescore
  8. 2026-09-26 00:26 UTCEPSS rescore
  9. 2026-09-20 20:15 UTCEPSS rescore
  10. 2026-09-20 20:15 UTCEPSS rescore
  11. 2026-09-19 13:02 UTCOSV refresh
  12. 2026-09-18 19:28 UTCEPSS rescore
  13. 2026-09-18 19:27 UTCEPSS rescore
  14. 2026-09-17 19:30 UTCEPSS rescore
  15. 2026-09-16 14:08 UTCEPSS rescore
  16. 2026-09-16 05:15 UTCEPSS rescore
  17. 2026-09-13 16:47 UTCEPSS rescore
  18. 2026-09-12 15:01 UTCEPSS rescore
  19. 2026-09-10 09:34 UTCEPSS rescore
  20. 2026-09-08 22:00 UTCEPSS rescore
  21. 2026-09-07 16:01 UTCEPSS rescore
  22. 2026-09-06 13:47 UTCEPSS rescore
  23. 2026-09-06 13:47 UTCEPSS rescore
  24. 2026-09-04 05:06 UTCEPSS rescore
  25. 2026-09-02 14:11 UTCEPSS rescore
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  1. 2026-09-01 13:53 UTCEPSS rescore
  2. 2026-09-01 04:39 UTCEPSS rescore
  3. 2026-09-01 04:39 UTCEPSS rescore
  4. 2026-08-31 16:34 UTCOSV refresh
  5. 2026-08-30 19:17 UTCEPSS rescore
  6. 2026-08-30 01:22 UTCEPSS rescore
  7. 2026-08-28 21:41 UTCEPSS rescore
  8. 2026-08-27 14:25 UTCEPSS rescore
  9. 2026-08-26 14:46 UTCEPSS rescore
  10. 2026-08-25 13:48 UTCEPSS rescore
  11. 2026-08-23 00:19 UTCEPSS rescore
  12. 2026-08-21 23:49 UTCEPSS rescore
  13. 2026-08-20 22:55 UTCEPSS rescore
  14. 2026-08-19 17:03 UTCEPSS rescore
  15. 2026-08-18 13:48 UTCEPSS rescore
  16. 2026-08-17 13:47 UTCEPSS rescore
  17. 2026-08-16 14:56 UTCEPSS rescore
  18. 2026-08-16 02:14 UTCEPSS rescore
  19. 2026-08-15 01:30 UTCEPSS rescore
  20. 2026-08-14 21:10 UTCVendor advisory
  21. 2026-08-14 08:57 UTCEG score recompute
  22. 2026-08-14 08:57 UTCVendor advisory
  23. 2026-08-13 22:00 UTCEPSS rescore
  24. 2026-08-13 00:56 UTCEG score recompute
  25. 2026-08-13 00:56 UTCVendor advisory
  26. 2026-08-12 13:50 UTCEPSS rescore
  27. 2026-08-11 23:51 UTCEG score recompute
  28. 2026-08-11 23:51 UTCVendor advisory
  29. 2026-08-11 13:42 UTCEPSS rescore
  30. 2026-08-11 06:16 UTCEG score recompute
  31. 2026-08-11 06:16 UTCVendor advisory
  32. 2026-08-11 00:00 UTCEPSS rescore
  33. 2026-08-10 08:42 UTCVendor advisory
  34. 2026-08-09 20:18 UTCEG score recompute
  35. 2026-08-09 20:18 UTCVendor advisory
  36. 2026-08-09 13:46 UTCEPSS rescore
  37. 2026-08-09 08:34 UTCEG score recompute
  38. 2026-08-09 08:34 UTCVendor advisory
  39. 2026-08-08 16:37 UTCEPSS rescore
  40. 2026-08-08 08:21 UTCVendor advisory
  41. 2026-08-07 20:37 UTCEG score recompute
  42. 2026-08-07 20:37 UTCVendor advisory
  43. 2026-08-06 13:46 UTCEPSS rescore
  44. 2026-08-06 02:58 UTCEG score recompute
  45. 2026-08-06 02:58 UTCVendor advisory
  46. 2026-08-05 19:17 UTCEPSS rescore
  47. 2026-08-04 15:10 UTCEPSS rescore
  48. 2026-08-04 05:00 UTCVendor advisory
  49. 2026-08-02 19:29 UTCEG score recompute
  50. 2026-08-02 19:29 UTCVendor advisory
  51. 2026-08-02 02:26 UTCEPSS rescore
  52. 2026-08-01 04:16 UTCEPSS rescore
  53. 2026-07-30 16:27 UTCEPSS rescore
  54. 2026-07-30 01:30 UTCEPSS rescore
  55. 2026-07-28 15:36 UTCEPSS rescore
  56. 2026-07-26 14:54 UTCEPSS rescore
  57. 2026-07-26 14:54 UTCEPSS rescore
  58. 2026-07-25 14:18 UTCEPSS rescore
  59. 2026-07-25 14:17 UTCEPSS rescore
  60. 2026-07-24 14:17 UTCEPSS rescore
  61. 2026-07-23 14:18 UTCEPSS rescore
  62. 2026-07-23 14:18 UTCEPSS rescore
  63. 2026-07-23 03:08 UTCEG score recompute
  64. 2026-07-22 14:08 UTCEPSS rescore
  65. 2026-07-22 14:08 UTCEPSS rescore
  66. 2026-07-22 13:37 UTCOSV refresh
  67. 2026-07-20 17:08 UTCEPSS rescore
  68. 2026-07-20 17:08 UTCEPSS rescore
  69. 2026-07-19 14:31 UTCEPSS rescore
  70. 2026-07-19 14:31 UTCEPSS rescore
  71. 2026-07-19 02:29 UTCEPSS rescore
  72. 2026-07-18 10:04 UTCEPSS rescore
  73. 2026-07-18 10:04 UTCEPSS rescore
  74. 2026-07-16 17:03 UTCEPSS rescore
  75. 2026-07-16 17:03 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2026-27959?
CVE-2026-27959 is a high vulnerability published on February 26, 2026. Koa is middleware for Node.js using ES2017 async functions. Prior to versions 3.1.2 and 2.16.4, Koa's ctx.hostname API performs naive parsing of the HTTP Host header, extracting everything before the first colon without validating the input conforms to RFC 3986 hostname syntax. When a malformed…
When was CVE-2026-27959 disclosed?
CVE-2026-27959 was first published on February 26, 2026, with the most recent update on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-27959 actively exploited?
CVE-2026-27959 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (42nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-27959?
CVE-2026-27959 has a CVSS base score of 7.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-27959?
A fix for CVE-2026-27959 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-27959 are linked in the Vendor Advisories panel on this page.

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