CVE-2026-66296 (GCVE-0-2026-66296)
Vulnerability from cvelistv5 – Published: 2026-08-03 19:04 – Updated: 2026-08-03 19:50
VLAI
EPSS
VEX
Title
Reflected XSS in oaskit's default HTML error handler
Summary
Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler.
Oaskit.ErrorHandler.Default.format_reason/4 and Oaskit.ErrorHandler.Default.reason_to_html/1 in lib/oaskit/error_handler/default.ex render request-validation failures as an HTML page whenever the request's Accept header contains html, interpolating request-controlled strings into that page without HTML escaping. The unescaped values are object keys taken from a request body or from an object or deepObject query parameter, which appear in the JSON Schema error's instance path when a schema rejects them (for example under additionalProperties: false), and the raw Content-Type header, reflected in unsupported-media-type errors when it fails to parse.
Because browsers send Accept: text/html on ordinary top-level navigation, a crafted GET link is sufficient to trigger the error page; no form submission, custom Content-Type, or attacker-controlled script on the victim's side is required. A payload such as filter[</code></h2><script>alert(document.domain)</script>]=x terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin's cookies, session, and same-origin responses.
Both HTML error rendering and the vulnerable handler are enabled by default: Oaskit.Plugs.ValidateRequest defaults :html_errors to true and :error_handler to Oaskit.ErrorHandler.Default, so applications following the documented usage are affected without any opt-in.
This issue affects oaskit: from 0.1.0 before 0.14.1.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
- CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/lud/oaskit/security/advisories… | vendor-advisoryrelated |
| https://cna.erlef.org/cves/CVE-2026-66296.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-66296 | related |
| https://github.com/lud/oaskit/commit/b70c6b2eaf0b… | patch |
Impacted products
Date Public
2026-07-05 00:00
Credits
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"value": "\u003cp\u003eImproper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler.\u003c/p\u003e\n\u003cp\u003e\u003ccode\u003eOaskit.ErrorHandler.Default.format_reason/4\u003c/code\u003e and \u003ccode\u003eOaskit.ErrorHandler.Default.reason_to_html/1\u003c/code\u003e in \u003ccode\u003elib/oaskit/error_handler/default.ex\u003c/code\u003e render request-validation failures as an HTML page whenever the request\u0027s \u003ccode\u003eAccept\u003c/code\u003e header contains \u003ccode\u003ehtml\u003c/code\u003e, interpolating request-controlled strings into that page without HTML escaping. The unescaped values are object keys taken from a request body or from an object or \u003ccode\u003edeepObject\u003c/code\u003e query parameter, which appear in the JSON Schema error\u0027s instance path when a schema rejects them (for example under \u003ccode\u003eadditionalProperties: false\u003c/code\u003e), and the raw \u003ccode\u003eContent-Type\u003c/code\u003e header, reflected in unsupported-media-type errors when it fails to parse.\u003c/p\u003e\n\u003cp\u003eBecause browsers send \u003ccode\u003eAccept: text/html\u003c/code\u003e on ordinary top-level navigation, a crafted GET link is sufficient to trigger the error page; no form submission, custom \u003ccode\u003eContent-Type\u003c/code\u003e, or attacker-controlled script on the victim\u0027s side is required. A payload such as \u003ccode\u003efilter[\u0026lt;/code\u0026gt;\u0026lt;/h2\u0026gt;\u0026lt;script\u0026gt;alert(document.domain)\u0026lt;/script\u0026gt;]=x\u003c/code\u003e terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin\u0027s cookies, session, and same-origin responses.\u003c/p\u003e\n\u003cp\u003eBoth HTML error rendering and the vulnerable handler are enabled by default: \u003ccode\u003eOaskit.Plugs.ValidateRequest\u003c/code\u003e defaults \u003ccode\u003e:html_errors\u003c/code\u003e to \u003ccode\u003etrue\u003c/code\u003e and \u003ccode\u003e:error_handler\u003c/code\u003e to \u003ccode\u003eOaskit.ErrorHandler.Default\u003c/code\u003e, so applications following the documented usage are affected without any opt-in.\u003c/p\u003e\n\u003cp\u003eThis issue affects oaskit: from 0.1.0 before 0.14.1.\u003c/p\u003e"
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"value": "Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler.\n\n`Oaskit.ErrorHandler.Default.format_reason/4` and `Oaskit.ErrorHandler.Default.reason_to_html/1` in `lib/oaskit/error_handler/default.ex` render request-validation failures as an HTML page whenever the request\u0027s `Accept` header contains `html`, interpolating request-controlled strings into that page without HTML escaping. The unescaped values are object keys taken from a request body or from an object or `deepObject` query parameter, which appear in the JSON Schema error\u0027s instance path when a schema rejects them (for example under `additionalProperties: false`), and the raw `Content-Type` header, reflected in unsupported-media-type errors when it fails to parse.\n\nBecause browsers send `Accept: text/html` on ordinary top-level navigation, a crafted GET link is sufficient to trigger the error page; no form submission, custom `Content-Type`, or attacker-controlled script on the victim\u0027s side is required. A payload such as `filter[\u003c/code\u003e\u003c/h2\u003e\u003cscript\u003ealert(document.domain)\u003c/script\u003e]=x` terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin\u0027s cookies, session, and same-origin responses.\n\nBoth HTML error rendering and the vulnerable handler are enabled by default: `Oaskit.Plugs.ValidateRequest` defaults `:html_errors` to `true` and `:error_handler` to `Oaskit.ErrorHandler.Default`, so applications following the documented usage are affected without any opt-in.\n\nThis issue affects oaskit: from 0.1.0 before 0.14.1."
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A payload such as filter[\u003c/code\u003e\u003c/h2\u003e\u003cscript\u003ealert(document.domain)\u003c/script\u003e]=x terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin\u0027s cookies, session, and same-origin responses.\\n\\nBoth HTML error rendering and the vulnerable handler are enabled by default: Oaskit.Plugs.ValidateRequest defaults :html_errors to true and :error_handler to Oaskit.ErrorHandler.Default, so applications following the documented usage are affected without any opt-in.\\n\\nThis issue affects oaskit: from 0.1.0 before 0.14.1.\"}],\"affected\":[{\"source\":\"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\",\"affectedData\":[{\"vendor\":\"lud\",\"product\":\"oaskit\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://repo.hex.pm\",\"packageName\":\"oaskit\",\"cpes\":[\"cpe:2.3:a:lud:oaskit:*:*:*:*:*:elixir:*:*\"],\"modules\":[\"Elixir.Oaskit.ErrorHandler.Default\"],\"programFiles\":[\"lib/oaskit/error_handler/default.ex\"],\"programRoutines\":[{\"name\":\"\u0027Elixir.Oaskit.ErrorHandler.Default\u0027:format_reason/4\"},{\"name\":\"\u0027Elixir.Oaskit.ErrorHandler.Default\u0027:reason_to_html/1\"}],\"repo\":\"https://github.com/lud/oaskit\",\"packageURL\":\"pkg:hex/oaskit\",\"versions\":[{\"version\":\"0.1.0\",\"lessThan\":\"0.14.1\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"lud\",\"product\":\"oaskit\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://github.com\",\"packageName\":\"lud/oaskit\",\"cpes\":[\"cpe:2.3:a:lud:oaskit:*:*:*:*:*:elixir:*:*\"],\"modules\":[\"Elixir.Oaskit.ErrorHandler.Default\"],\"programFiles\":[\"lib/oaskit/error_handler/default.ex\"],\"programRoutines\":[{\"name\":\"\u0027Elixir.Oaskit.ErrorHandler.Default\u0027:format_reason/4\"},{\"name\":\"\u0027Elixir.Oaskit.ErrorHandler.Default\u0027:reason_to_html/1\"}],\"repo\":\"https://github.com/lud/oaskit\",\"packageURL\":\"pkg:github/lud/oaskit\",\"versions\":[{\"version\":\"552de8ca0ff60617bea58bcafa451892d61a161c\",\"lessThan\":\"b70c6b2eaf0b11bdd0bbb21b8a87dbb3d46918a1\",\"versionType\":\"git\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"4.0\",\"vectorString\":\"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X\",\"baseScore\":5.1,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"attackRequirements\":\"NONE\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"ACTIVE\",\"vulnConfidentialityImpact\":\"NONE\",\"vulnIntegrityImpact\":\"NONE\",\"vulnAvailabilityImpact\":\"NONE\",\"subConfidentialityImpact\":\"LOW\",\"subIntegrityImpact\":\"LOW\",\"subAvailabilityImpact\":\"NONE\",\"exploitMaturity\":\"NOT_DEFINED\",\"confidentialityRequirement\":\"NOT_DEFINED\",\"integrityRequirement\":\"NOT_DEFINED\",\"availabilityRequirement\":\"NOT_DEFINED\",\"modifiedAttackVector\":\"NOT_DEFINED\",\"modifiedAttackComplexity\":\"NOT_DEFINED\",\"modifiedAttackRequirements\":\"NOT_DEFINED\",\"modifiedPrivilegesRequired\":\"NOT_DEFINED\",\"modifiedUserInteraction\":\"NOT_DEFINED\",\"modifiedVulnConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedVulnIntegrityImpact\":\"NOT_DEFINED\",\"modifiedVulnAvailabilityImpact\":\"NOT_DEFINED\",\"modifiedSubConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedSubIntegrityImpact\":\"NOT_DEFINED\",\"modifiedSubAvailabilityImpact\":\"NOT_DEFINED\",\"Safety\":\"NOT_DEFINED\",\"Automatable\":\"NOT_DEFINED\",\"Recovery\":\"NOT_DEFINED\",\"valueDensity\":\"NOT_DEFINED\",\"vulnerabilityResponseEffort\":\"NOT_DEFINED\",\"providerUrgency\":\"NOT_DEFINED\"}}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-08-03T19:50:03.665445Z\",\"id\":\"CVE-2026-66296\",\"options\":[{\"exploitation\":\"poc\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-79\"}]}],\"references\":[{\"url\":\"https://cna.erlef.org/cves/CVE-2026-66296.html\",\"source\":\"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\"},{\"url\":\"https://github.com/lud/oaskit/commit/b70c6b2eaf0b11bdd0bbb21b8a87dbb3d46918a1\",\"source\":\"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\"},{\"url\":\"https://github.com/lud/oaskit/security/advisories/GHSA-h7xw-x8wr-xpcc\",\"source\":\"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\"},{\"url\":\"https://osv.dev/vulnerability/EEF-CVE-2026-66296\",\"source\":\"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\"},{\"url\":\"https://github.com/lud/oaskit/security/advisories/GHSA-h7xw-x8wr-xpcc\",\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\"}]}}",
"vulnrichment": {
"containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-66296\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"poc\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-08-03T19:50:03.665445Z\"}}}], \"references\": [{\"url\": \"https://github.com/lud/oaskit/security/advisories/GHSA-h7xw-x8wr-xpcc\", \"tags\": [\"exploit\"]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-08-03T19:50:23.782Z\"}}], \"cna\": {\"title\": \"Reflected XSS in oaskit\u0027s default HTML error handler\", \"source\": {\"discovery\": \"INTERNAL\"}, \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"Ludovic Dem\"}, {\"lang\": \"en\", \"type\": \"remediation developer\", \"value\": \"Ludovic Dem\"}, {\"lang\": \"en\", \"type\": \"analyst\", \"value\": \"Jonatan M\\u00e4nnchen / EEF\"}], \"impacts\": [{\"capecId\": \"CAPEC-591\", \"descriptions\": [{\"lang\": \"en\", \"value\": \"CAPEC-591 Reflected XSS\"}]}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"Safety\": \"NOT_DEFINED\", \"version\": \"4.0\", \"Recovery\": \"NOT_DEFINED\", \"baseScore\": 5.1, \"Automatable\": \"NOT_DEFINED\", \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"valueDensity\": \"NOT_DEFINED\", \"vectorString\": \"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N\", \"providerUrgency\": \"NOT_DEFINED\", \"userInteraction\": \"ACTIVE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"NONE\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"LOW\", \"vulnIntegrityImpact\": \"NONE\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"NONE\", \"subConfidentialityImpact\": \"LOW\", \"vulnConfidentialityImpact\": \"NONE\", \"vulnerabilityResponseEffort\": \"NOT_DEFINED\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"cpes\": [\"cpe:2.3:a:lud:oaskit:*:*:*:*:*:elixir:*:*\"], \"repo\": \"https://github.com/lud/oaskit\", \"vendor\": \"lud\", \"modules\": [\"Elixir.Oaskit.ErrorHandler.Default\"], \"product\": \"oaskit\", \"versions\": [{\"status\": \"affected\", \"version\": \"0.1.0\", \"lessThan\": \"0.14.1\", \"versionType\": \"semver\"}], \"packageURL\": \"pkg:hex/oaskit\", \"packageName\": \"oaskit\", \"programFiles\": [\"lib/oaskit/error_handler/default.ex\"], \"collectionURL\": \"https://repo.hex.pm\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"\u0027Elixir.Oaskit.ErrorHandler.Default\u0027:format_reason/4\"}, {\"name\": \"\u0027Elixir.Oaskit.ErrorHandler.Default\u0027:reason_to_html/1\"}]}, {\"cpes\": [\"cpe:2.3:a:lud:oaskit:*:*:*:*:*:elixir:*:*\"], \"repo\": \"https://github.com/lud/oaskit\", \"vendor\": \"lud\", \"modules\": [\"Elixir.Oaskit.ErrorHandler.Default\"], \"product\": \"oaskit\", \"versions\": [{\"status\": \"affected\", \"version\": \"552de8ca0ff60617bea58bcafa451892d61a161c\", \"lessThan\": \"b70c6b2eaf0b11bdd0bbb21b8a87dbb3d46918a1\", \"versionType\": \"git\"}], \"packageURL\": \"pkg:github/lud/oaskit\", \"packageName\": \"lud/oaskit\", \"programFiles\": [\"lib/oaskit/error_handler/default.ex\"], \"collectionURL\": \"https://github.com\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"\u0027Elixir.Oaskit.ErrorHandler.Default\u0027:format_reason/4\"}, {\"name\": \"\u0027Elixir.Oaskit.ErrorHandler.Default\u0027:reason_to_html/1\"}]}], \"datePublic\": \"2026-07-05T00:00:00.000Z\", \"references\": [{\"url\": \"https://github.com/lud/oaskit/security/advisories/GHSA-h7xw-x8wr-xpcc\", \"tags\": [\"vendor-advisory\", \"related\"]}, {\"url\": \"https://cna.erlef.org/cves/CVE-2026-66296.html\", \"tags\": [\"related\"]}, {\"url\": \"https://osv.dev/vulnerability/EEF-CVE-2026-66296\", \"tags\": [\"related\"]}, {\"url\": \"https://github.com/lud/oaskit/commit/b70c6b2eaf0b11bdd0bbb21b8a87dbb3d46918a1\", \"tags\": [\"patch\"]}], \"workarounds\": [{\"lang\": \"en\", \"value\": \"Disable HTML error rendering so that validation failures are returned as JSON only:\\n\\nplug Oaskit.Plugs.ValidateRequest, html_errors: false\\n\\nThis prevents the vulnerable HTML page from being rendered at all, on any oaskit version. Alternatively, configure a custom :error_handler that does not emit HTML built from request-derived values.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eDisable HTML error rendering so that validation failures are returned as JSON only:\u003c/p\u003e\\n\u003cpre\u003e\u003ccode class=\\\"language-elixir\\\"\u003eplug Oaskit.Plugs.ValidateRequest, html_errors: false\\n\u003c/code\u003e\u003c/pre\u003e\\n\u003cp\u003eThis prevents the vulnerable HTML page from being rendered at all, on any oaskit version. Alternatively, configure a custom \u003ccode\u003e:error_handler\u003c/code\u003e that does not emit HTML built from request-derived values.\u003c/p\u003e\", \"base64\": false}, {\"type\": \"text/markdown\", \"value\": \"Disable HTML error rendering so that validation failures are returned as JSON only:\\n\\n```elixir\\nplug Oaskit.Plugs.ValidateRequest, html_errors: false\\n```\\n\\nThis prevents the vulnerable HTML page from being rendered at all, on any oaskit version. Alternatively, configure a custom `:error_handler` that does not emit HTML built from request-derived values.\", \"base64\": false}]}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler.\\n\\nOaskit.ErrorHandler.Default.format_reason/4 and Oaskit.ErrorHandler.Default.reason_to_html/1 in lib/oaskit/error_handler/default.ex render request-validation failures as an HTML page whenever the request\u0027s Accept header contains html, interpolating request-controlled strings into that page without HTML escaping. The unescaped values are object keys taken from a request body or from an object or deepObject query parameter, which appear in the JSON Schema error\u0027s instance path when a schema rejects them (for example under additionalProperties: false), and the raw Content-Type header, reflected in unsupported-media-type errors when it fails to parse.\\n\\nBecause browsers send Accept: text/html on ordinary top-level navigation, a crafted GET link is sufficient to trigger the error page; no form submission, custom Content-Type, or attacker-controlled script on the victim\u0027s side is required. A payload such as filter[\u003c/code\u003e\u003c/h2\u003e\u003cscript\u003ealert(document.domain)\u003c/script\u003e]=x terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin\u0027s cookies, session, and same-origin responses.\\n\\nBoth HTML error rendering and the vulnerable handler are enabled by default: Oaskit.Plugs.ValidateRequest defaults :html_errors to true and :error_handler to Oaskit.ErrorHandler.Default, so applications following the documented usage are affected without any opt-in.\\n\\nThis issue affects oaskit: from 0.1.0 before 0.14.1.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eImproper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler.\u003c/p\u003e\\n\u003cp\u003e\u003ccode\u003eOaskit.ErrorHandler.Default.format_reason/4\u003c/code\u003e and \u003ccode\u003eOaskit.ErrorHandler.Default.reason_to_html/1\u003c/code\u003e in \u003ccode\u003elib/oaskit/error_handler/default.ex\u003c/code\u003e render request-validation failures as an HTML page whenever the request\u0027s \u003ccode\u003eAccept\u003c/code\u003e header contains \u003ccode\u003ehtml\u003c/code\u003e, interpolating request-controlled strings into that page without HTML escaping. The unescaped values are object keys taken from a request body or from an object or \u003ccode\u003edeepObject\u003c/code\u003e query parameter, which appear in the JSON Schema error\u0027s instance path when a schema rejects them (for example under \u003ccode\u003eadditionalProperties: false\u003c/code\u003e), and the raw \u003ccode\u003eContent-Type\u003c/code\u003e header, reflected in unsupported-media-type errors when it fails to parse.\u003c/p\u003e\\n\u003cp\u003eBecause browsers send \u003ccode\u003eAccept: text/html\u003c/code\u003e on ordinary top-level navigation, a crafted GET link is sufficient to trigger the error page; no form submission, custom \u003ccode\u003eContent-Type\u003c/code\u003e, or attacker-controlled script on the victim\u0027s side is required. A payload such as \u003ccode\u003efilter[\u0026lt;/code\u0026gt;\u0026lt;/h2\u0026gt;\u0026lt;script\u0026gt;alert(document.domain)\u0026lt;/script\u0026gt;]=x\u003c/code\u003e terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin\u0027s cookies, session, and same-origin responses.\u003c/p\u003e\\n\u003cp\u003eBoth HTML error rendering and the vulnerable handler are enabled by default: \u003ccode\u003eOaskit.Plugs.ValidateRequest\u003c/code\u003e defaults \u003ccode\u003e:html_errors\u003c/code\u003e to \u003ccode\u003etrue\u003c/code\u003e and \u003ccode\u003e:error_handler\u003c/code\u003e to \u003ccode\u003eOaskit.ErrorHandler.Default\u003c/code\u003e, so applications following the documented usage are affected without any opt-in.\u003c/p\u003e\\n\u003cp\u003eThis issue affects oaskit: from 0.1.0 before 0.14.1.\u003c/p\u003e\", \"base64\": false}, {\"type\": \"text/markdown\", \"value\": \"Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in lud oaskit allows reflected cross-site scripting via the default HTML error handler.\\n\\n`Oaskit.ErrorHandler.Default.format_reason/4` and `Oaskit.ErrorHandler.Default.reason_to_html/1` in `lib/oaskit/error_handler/default.ex` render request-validation failures as an HTML page whenever the request\u0027s `Accept` header contains `html`, interpolating request-controlled strings into that page without HTML escaping. The unescaped values are object keys taken from a request body or from an object or `deepObject` query parameter, which appear in the JSON Schema error\u0027s instance path when a schema rejects them (for example under `additionalProperties: false`), and the raw `Content-Type` header, reflected in unsupported-media-type errors when it fails to parse.\\n\\nBecause browsers send `Accept: text/html` on ordinary top-level navigation, a crafted GET link is sufficient to trigger the error page; no form submission, custom `Content-Type`, or attacker-controlled script on the victim\u0027s side is required. A payload such as `filter[\u003c/code\u003e\u003c/h2\u003e\u003cscript\u003ealert(document.domain)\u003c/script\u003e]=x` terminates the enclosing markup and the injected script executes in the origin of the application using oaskit, giving it access to that origin\u0027s cookies, session, and same-origin responses.\\n\\nBoth HTML error rendering and the vulnerable handler are enabled by default: `Oaskit.Plugs.ValidateRequest` defaults `:html_errors` to `true` and `:error_handler` to `Oaskit.ErrorHandler.Default`, so applications following the documented usage are affected without any opt-in.\\n\\nThis issue affects oaskit: from 0.1.0 before 0.14.1.\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-79\", \"description\": \"CWE-79 Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)\"}]}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:a:lud:oaskit:*:*:*:*:*:elixir:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"0.14.1\", \"versionStartIncluding\": \"0.1.0\"}], \"operator\": \"OR\"}], \"operator\": \"AND\"}], \"providerMetadata\": {\"orgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"shortName\": \"EEF\", \"dateUpdated\": \"2026-08-03T19:04:30.556Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-66296\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-03T19:50:27.860Z\", \"dateReserved\": \"2026-07-24T14:10:01.114Z\", \"assignerOrgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"datePublished\": \"2026-08-03T19:04:30.556Z\", \"assignerShortName\": \"EEF\"}",
"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.
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