CVE-2026-39823 (GCVE-0-2026-39823)
Vulnerability from cvelistv5 – Published: 2026-05-07 19:41 – Updated: 2026-05-08 14:05
VLAI?
Title
Bypass of meta content URL escaping causes XSS in html/template
Summary
CVE-2026-27142 fixed a vulnerability in which URLs were not correctly escaped inside of a <meta> tag's <content> attribute. If the URL content were to insert ASCII whitespaces around the '=' rune inside of the <content> attribute, the escaper would fail to similarly escape it, leading to XSS.
Severity ?
6.1 (Medium)
CWE
- CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Assigner
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Go standard library | html/template |
Affected:
0 , < 1.25.10
(semver)
Affected: 1.26.0-0 , < 1.26.3 (semver) |
Credits
{
"containers": {
"adp": [
{
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 6.1,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "LOW",
"integrityImpact": "LOW",
"privilegesRequired": "NONE",
"scope": "CHANGED",
"userInteraction": "REQUIRED",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
"version": "3.1"
}
},
{
"other": {
"content": {
"id": "CVE-2026-39823",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-05-08T14:05:34.310805Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-05-08T14:05:55.152Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://pkg.go.dev",
"defaultStatus": "unaffected",
"packageName": "html/template",
"product": "html/template",
"programRoutines": [
{
"name": "tMetaContent"
},
{
"name": "Template.Execute"
},
{
"name": "Template.ExecuteTemplate"
}
],
"vendor": "Go standard library",
"versions": [
{
"lessThan": "1.25.10",
"status": "affected",
"version": "0",
"versionType": "semver"
},
{
"lessThan": "1.26.3",
"status": "affected",
"version": "1.26.0-0",
"versionType": "semver"
}
]
}
],
"credits": [
{
"lang": "en",
"value": "Samy Ghannad"
}
],
"descriptions": [
{
"lang": "en",
"value": "CVE-2026-27142 fixed a vulnerability in which URLs were not correctly escaped inside of a \u003cmeta\u003e tag\u0027s \u003ccontent\u003e attribute. If the URL content were to insert ASCII whitespaces around the \u0027=\u0027 rune inside of the \u003ccontent\u003e attribute, the escaper would fail to similarly escape it, leading to XSS."
}
],
"problemTypes": [
{
"descriptions": [
{
"description": "CWE-79: Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)",
"lang": "en"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-05-07T19:41:19.524Z",
"orgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
"shortName": "Go"
},
"references": [
{
"url": "https://go.dev/issue/78913"
},
{
"url": "https://go.dev/cl/769920"
},
{
"url": "https://groups.google.com/g/golang-announce/c/qcCIEXso47M"
},
{
"url": "https://pkg.go.dev/vuln/GO-2026-4982"
}
],
"title": "Bypass of meta content URL escaping causes XSS in html/template"
}
},
"cveMetadata": {
"assignerOrgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
"assignerShortName": "Go",
"cveId": "CVE-2026-39823",
"datePublished": "2026-05-07T19:41:19.524Z",
"dateReserved": "2026-04-07T18:13:03.527Z",
"dateUpdated": "2026-05-08T14:05:55.152Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-39823",
"date": "2026-05-09",
"epss": "0.00013",
"percentile": "0.02192"
},
"nvd": "{\"cve\":{\"id\":\"CVE-2026-39823\",\"sourceIdentifier\":\"security@golang.org\",\"published\":\"2026-05-07T20:16:43.290\",\"lastModified\":\"2026-05-08T15:16:37.500\",\"vulnStatus\":\"Undergoing Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"CVE-2026-27142 fixed a vulnerability in which URLs were not correctly escaped inside of a \u003cmeta\u003e tag\u0027s \u003ccontent\u003e attribute. If the URL content were to insert ASCII whitespaces around the \u0027=\u0027 rune inside of the \u003ccontent\u003e attribute, the escaper would fail to similarly escape it, leading to XSS.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N\",\"baseScore\":6.1,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"REQUIRED\",\"scope\":\"CHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"LOW\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":2.8,\"impactScore\":2.7}]},\"references\":[{\"url\":\"https://go.dev/cl/769920\",\"source\":\"security@golang.org\"},{\"url\":\"https://go.dev/issue/78913\",\"source\":\"security@golang.org\"},{\"url\":\"https://groups.google.com/g/golang-announce/c/qcCIEXso47M\",\"source\":\"security@golang.org\"},{\"url\":\"https://pkg.go.dev/vuln/GO-2026-4982\",\"source\":\"security@golang.org\"}]}}",
"vulnrichment": {
"containers": "{\"cna\": {\"title\": \"Bypass of meta content URL escaping causes XSS in html/template\", \"credits\": [{\"lang\": \"en\", \"value\": \"Samy Ghannad\"}], \"affected\": [{\"vendor\": \"Go standard library\", \"product\": \"html/template\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"lessThan\": \"1.25.10\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"1.26.0-0\", \"lessThan\": \"1.26.3\", \"versionType\": \"semver\"}], \"packageName\": \"html/template\", \"collectionURL\": \"https://pkg.go.dev\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"tMetaContent\"}, {\"name\": \"Template.Execute\"}, {\"name\": \"Template.ExecuteTemplate\"}]}], \"references\": [{\"url\": \"https://go.dev/issue/78913\"}, {\"url\": \"https://go.dev/cl/769920\"}, {\"url\": \"https://groups.google.com/g/golang-announce/c/qcCIEXso47M\"}, {\"url\": \"https://pkg.go.dev/vuln/GO-2026-4982\"}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"CVE-2026-27142 fixed a vulnerability in which URLs were not correctly escaped inside of a \u003cmeta\u003e tag\u0027s \u003ccontent\u003e attribute. If the URL content were to insert ASCII whitespaces around the \u0027=\u0027 rune inside of the \u003ccontent\u003e attribute, the escaper would fail to similarly escape it, leading to XSS.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"description\": \"CWE-79: Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)\"}]}], \"providerMetadata\": {\"orgId\": \"1bb62c36-49e3-4200-9d77-64a1400537cc\", \"shortName\": \"Go\", \"dateUpdated\": \"2026-05-07T19:41:19.524Z\"}}, \"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"cvssV3_1\": {\"scope\": \"CHANGED\", \"version\": \"3.1\", \"baseScore\": 6.1, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N\", \"integrityImpact\": \"LOW\", \"userInteraction\": \"REQUIRED\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"NONE\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"LOW\"}}, {\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-39823\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-05-08T14:05:34.310805Z\"}}}], \"providerMetadata\": {\"shortName\": \"CISA-ADP\", \"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"dateUpdated\": \"2026-05-08T14:05:50.846Z\"}}]}",
"cveMetadata": "{\"cveId\": \"CVE-2026-39823\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-07T19:41:19.524Z\", \"dateReserved\": \"2026-04-07T18:13:03.527Z\", \"assignerOrgId\": \"1bb62c36-49e3-4200-9d77-64a1400537cc\", \"datePublished\": \"2026-05-07T19:41:19.524Z\", \"assignerShortName\": \"Go\"}",
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
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.
Loading…
Loading…