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01 Record

CVE-2026-27959

Koa has Host Header Injection via `ctx.hostname`

HighPUBLISHEDCNA: GitHub_M
CNA base score7.5 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
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02 Description

Koa has Host Header Injection via `ctx.hostname`

03 Exploitation and scoring

Exploitation
Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.
SSVC decision
  • ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
  • AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
  • Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
0.39% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 32.9% of scored records. A rank, not a probability.
NVD base score
7.5 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD analysis status
Modified. NVD last modified this record on 2026-07-15.
Red Hat severity
Important. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2026-02-26 01:45Z8 MO AGO
Last updated
2026-07-15 01:12Z3 MO AGO
Reserved
2026-02-25
Assigning CNA
GitHub_M
Record state
PUBLISHED
Severity
High (CVSS 7.5)
CNA CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weaknesses
  • CWE-20Improper Input ValidationClass
Data version
5.2
Document digest
0a4f72fc941e800b22324dabeb2620f077f9afb50079b63d77777dc6d748197b

05 Affected products

VendorProductVersionsPlatforms
koajskoa>= 3.0.0, < 3.1.2, < 2.16.4—

06 References