CVE-2026-27959

HIGHPre-NVD 7.57.5
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-02-26. A secondary CVSS source baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
Trending — 4 sources updated this weekElevated

Also known asEUVD-2026-8816 (ENISA EUVD) · GHSA-7gcc-r8m5-44qm (GitHub Security Advisories)Source: ENISA EUVD

7.5EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 7.5Exploit: No code on recordExposed 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 impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity75% × 45%
Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.4%
EPSS %ILE
33rd
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.

EG Severity
7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

February 26, 2026

Last Modified

July 15, 2026

Advisory Details (3)

Auto-updated Jun 16, 2026
Patch available. Sources: github_commit, github.
GitHub advisoryMentions a patch (unverified)

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(4)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
redhatrhoai/odh-mod-arch-model-registry-rhel9:17767421412026-04-23redhat
redhatopenshift4/ose-monitoring-plugin-rhel9:17755771922026-04-16redhat
npmkoa @ 3.1.2 (fixes >= 3.0.0, < 3.1.2)—ghsa
npmkoa @ 2.16.4 (fixes < 2.16.4)—ghsa

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(2)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 42× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 96 of 186 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 4 repeat rows among the latest 100 are merged into the row they repeat. The 90 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  2. 2026-11-01 07:55 UTCGHSA enrichmentGHSA-7gcc-r8m5-44qm · GitHub severity HIGH · GitHub CVSS 7.5
  3. 2026-11-01 07:55 UTCEG score recompute
  4. 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  5. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  6. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  7. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  8. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  9. 2026-10-27 11:13 UTCEG score recompute
  10. 2026-10-27 11:13 UTCVendor advisory
  11. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  12. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.4% · 32nd percentile
  13. 2026-10-25 14:38 UTCEG score recompute
  14. 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.6% · 47th percentile
  15. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  16. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  17. 2026-10-21 16:32 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  18. 2026-10-20 16:32 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  19. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  20. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  21. 2026-10-18 03:50 UTCEG score recompute
  22. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  23. 2026-10-17 16:23 UTCEG score recompute
  24. 2026-10-17 16:23 UTCVendor advisory
  25. 2026-10-16 16:41 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
Show 71 more
  1. 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  2. 2026-10-14 16:32 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  3. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  4. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  5. 2026-10-12 16:17 UTCEG score recompute
  6. 2026-10-11 19:59 UTCEG score recompute
  7. 2026-10-11 17:12 UTCEG score recompute
  8. 2026-10-11 14:43 UTCEG score recompute
  9. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  10. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  11. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  12. 2026-10-09 05:55 UTCOSV refresh
  13. 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  14. 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  15. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  16. 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  17. 2026-10-04 23:21 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  18. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  19. 2026-10-01 19:49 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  20. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  21. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  22. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  23. 2026-09-26 00:26 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  24. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  25. 2026-09-19 13:02 UTCOSV refresh
  26. 2026-09-18 19:27 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  27. 2026-09-17 19:30 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  28. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  29. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  30. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  31. 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  32. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  33. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  34. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  35. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  36. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  37. 2026-09-02 14:11 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  38. 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  39. 2026-09-01 04:39 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  40. 2026-08-31 16:34 UTCOSV refresh
  41. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  42. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  43. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  44. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  45. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  46. 2026-08-25 13:48 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  47. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  48. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  49. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  50. 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  51. 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  52. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  53. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  54. 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  55. 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  56. 2026-08-14 21:10 UTCVendor advisory
  57. 2026-08-14 08:57 UTCEG score recompute
  58. 2026-08-14 08:57 UTCVendor advisory
  59. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  60. 2026-08-13 00:56 UTCEG score recompute
  61. 2026-08-13 00:56 UTCVendor advisory
  62. 2026-08-12 13:50 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  63. 2026-08-11 23:51 UTCEG score recompute
  64. 2026-08-11 23:51 UTCVendor advisory
  65. 2026-08-11 13:42 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  66. 2026-08-11 06:16 UTCEG score recompute
  67. 2026-08-11 06:16 UTCVendor advisory
  68. 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  69. 2026-08-10 08:42 UTCVendor advisory
  70. 2026-08-09 20:18 UTCEG score recompute
  71. 2026-08-09 20:18 UTCVendor advisory

Frequently asked(5)

What is CVE-2026-27959?
CVE-2026-27959 is a high-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-27959 published?
The CVE record for CVE-2026-27959 was published on February 26, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of July 15, 2026; the record at its source may have been updated since.
Is CVE-2026-27959 actively exploited?
CVE-2026-27959 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (33rd 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.

Dependency Blast Radius

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