CVE-2026-27959 (GCVE-0-2026-27959)
Vulnerability from cvelistv5 – Published: 2026-02-26 01:45 – Updated: 2026-07-15 01:12
VLAI
EPSS
VEX
Title
Koa has Host Header Injection via `ctx.hostname`
Summary
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.
Severity
7.5 (High)
8.2 (High)
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-02-26 19:31 UTC
CWE
- CWE-20 - Improper Input Validation
Assigner
References
8 references
| URL | Tags |
|---|---|
| https://github.com/koajs/koa/security/advisories/… | x_refsource_CONFIRM |
| https://github.com/koajs/koa/commit/55ab9bab044ea… | x_refsource_MISC |
| https://github.com/koajs/koa/commit/b76ddc01fdb70… | x_refsource_MISC |
| https://access.redhat.com/security/cve/CVE-2026-27959 | vdb-entryx_refsource_REDHAT |
| https://bugzilla.redhat.com/show_bug.cgi?id=2442928 | issue-trackingx_refsource_REDHAT |
| https://security.access.redhat.com/data/csaf/v2/v… | x_sadp-csaf-vex |
| https://access.redhat.com/errata/RHSA-2026:10184 | vendor-advisoryx_refsource_REDHAT |
| https://access.redhat.com/errata/RHSA-2026:7249 | vendor-advisoryx_refsource_REDHAT |
Impacted products
8 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| koajs | koa |
Affected:
>= 3.0.0, < 3.1.2
Affected: < 2.16.4 |
guessed | |
| Red Hat | Red Hat OpenShift AI 2.25 |
Unaffected:
1776742021 , < *
(rpm)
cpe:/a:redhat:openshift_ai:2.25::el9 |
||
| Red Hat | Red Hat OpenShift AI 2.25 |
Unaffected:
1776742141 , < *
(rpm)
cpe:/a:redhat:openshift_ai:2.25::el9 |
||
| Red Hat | Red Hat OpenShift Container Platform 4.19 |
Unaffected:
1775577192 , < *
(rpm)
cpe:/a:redhat:openshift:4.19::el9 |
||
| Red Hat | Red Hat Developer Hub |
cpe:/a:redhat:rhdh:1
|
||
| Red Hat | Red Hat OpenShift AI (RHOAI) |
cpe:/a:redhat:openshift_ai
|
||
| Red Hat | Red Hat OpenShift Dev Spaces |
cpe:/a:redhat:openshift_devspaces:3
|
||
| Red Hat | Self-service automation portal 2 |
cpe:/a:redhat:ansible_portal:2
|
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"sourceIdentifier": "security-advisories@github.com",
"vulnStatus": "Modified",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-20"
}
],
"source": "security-advisories@github.com",
"type": "Secondary"
},
{
"description": [
{
"lang": "en",
"value": "NVD-CWE-noinfo"
}
],
"source": "nvd@nist.gov",
"type": "Secondary"
},
{
"description": [
{
"lang": "en",
"value": "CWE-20"
}
],
"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c",
"type": "Secondary"
}
]
}
},
"redhat_vex": {
"aggregate_severity": "Important",
"current_release_date": "2026-06-30T04:03:23+00:00",
"cve": "CVE-2026-27959",
"id": "CVE-2026-27959",
"initial_release_date": "2026-02-26T01:45:45.668000+00:00",
"product_status:fixed": "12",
"product_status:known_affected": "3",
"product_status:known_not_affected": "855",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "koa: Koa: Host header injection vulnerability due to malformed HTTP Host header parsing",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27959.json",
"version": "3"
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-27959",
"options": [
{
"Exploitation": "poc"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-02-26T19:31:17.215940Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-02-26T19:31:35.224Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "koa",
"vendor": "koajs",
"versions": [
{
"status": "affected",
"version": "\u003e= 3.0.0, \u003c 3.1.2"
},
{
"status": "affected",
"version": "\u003c 2.16.4"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "Koa is middleware for Node.js using ES2017 async functions. Prior to versions 3.1.2 and 2.16.4, Koa\u0027s `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."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 7.5,
"baseSeverity": "HIGH",
"confidentialityImpact": "NONE",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-20",
"description": "CWE-20: Improper Input Validation",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-02-26T01:45:45.668Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/koajs/koa/security/advisories/GHSA-7gcc-r8m5-44qm",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/koajs/koa/security/advisories/GHSA-7gcc-r8m5-44qm"
},
{
"name": "https://github.com/koajs/koa/commit/55ab9bab044ead4e82c70a30a4f9dc0fc9c1b6df",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/koajs/koa/commit/55ab9bab044ead4e82c70a30a4f9dc0fc9c1b6df"
},
{
"name": "https://github.com/koajs/koa/commit/b76ddc01fdb703e51652b0fd131d16394cadcfeb",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/koajs/koa/commit/b76ddc01fdb703e51652b0fd131d16394cadcfeb"
}
],
"source": {
"advisory": "GHSA-7gcc-r8m5-44qm",
"discovery": "UNKNOWN"
},
"title": "Koa has Host Header Injection via `ctx.hostname`"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-27959",
"datePublished": "2026-02-26T01:45:45.668Z",
"dateReserved": "2026-02-25T03:24:57.792Z",
"dateUpdated": "2026-02-26T19:32:00.105Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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