CVE-2026-58391
OPNsense is a FreeBSD based firewall and routing platform. Prior to version 26.1.11, Firewall Rules and NAT views place stored category names and alias descriptions into HTML title attributes in filter_rule.volt and nat_rule.volt without quote-safe encoding. The response layer uses ENT_NOQUOTES, so a double quote survives and closes the attribute, allowing an event-handler attribute to be added to the existing span.
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A user with Firewall Categories or Firewall Alias Edit privileges can store a category name or alias description; the category must be assigned to a filter or NAT rule, or the alias must be referenced by a rule source or destination, and the rule must be saved so the affected tooltip is rendered. Script then executes in the session of an administrator or other user who opens the affected Rules or NAT page. The script can access CSRF material and perform authenticated actions as the victim. This issue is fixed in version 26.1.11.
CVSS
- Base score
- 5.4
- Version
- 3.1
- Vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days
- 0.21 %
- Percentile among all scored CVEs
- 11
- Score date
- 10/20/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
ATT&CK techniques
How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.
- Exploitation
T1189Drive-by Compromiseinitial access95 % - Primary impact
T1059.007JavaScriptexecution90 % - Secondary impact
T1185Browser Session Hijackingcollection55 %
XSS almacenado: el vector de atributo HTML sin codificación con ENT_NOQUOTES ejecuta JavaScript en el navegador del administrador que abre Rules/NAT, con acceso a CSRF y acciones autenticadas.
Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.
ATT&CK mitigations that cover these techniques
Affected technologies (1)
⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.
CWEs
- CWE-79, CWE-83
References
Show 5 references
- https://github.com/opnsense/core/commit/5e6313f50546474031805039e209830b63b2b0e4
- https://github.com/opnsense/core/commit/fb3b8a07f407ce281b1dde748706acbb0bc514ce
- https://github.com/opnsense/core/security/advisories/GHSA-2xrm-p255-p43h
- https://hackerask.com/posts/opnsense
- https://github.com/opnsense/core/security/advisories/GHSA-2xrm-p255-p43h
Raw JSON (NVD)
Show
{
"id": "CVE-2026-58391",
"cveTags": [],
"metrics": {
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-58391",
"role": "CISA Coordinator",
"options": [
{
"exploitation": "poc"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"version": "2.0.3",
"timestamp": "2026-10-20T02:42:27.132294Z"
}
}
],
"cvssMetricV31": [
{
"type": "Secondary",
"source": "security-advisories@github.com",
"cvssData": {
"scope": "CHANGED",
"version": "3.1",
"baseScore": 5.4,
"attackVector": "NETWORK",
"baseSeverity": "MEDIUM",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
"integrityImpact": "LOW",
"userInteraction": "REQUIRED",
"attackComplexity": "LOW",
"availabilityImpact": "NONE",
"privilegesRequired": "LOW",
"confidentialityImpact": "LOW"
},
"impactScore": 2.7,
"exploitabilityScore": 2.3
}
]
},
"affected": [
{
"source": "security-advisories@github.com",
"affectedData": [
{
"vendor": "opnsense",
"product": "core",
"versions": [
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"version": "< 26.1.11"
}
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],
"published": "2026-10-15T16:18:18.030",
"references": [
{
"url": "https://github.com/opnsense/core/commit/5e6313f50546474031805039e209830b63b2b0e4",
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{
"url": "https://hackerask.com/posts/opnsense",
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"weaknesses": [
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"source": "security-advisories@github.com",
"description": [
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],
"descriptions": [
{
"lang": "en",
"value": "OPNsense is a FreeBSD based firewall and routing platform. Prior to version 26.1.11, Firewall Rules and NAT views place stored category names and alias descriptions into HTML title attributes in filter_rule.volt and nat_rule.volt without quote-safe encoding. The response layer uses ENT_NOQUOTES, so a double quote survives and closes the attribute, allowing an event-handler attribute to be added to the existing span. A user with Firewall Categories or Firewall Alias Edit privileges can store a category name or alias description; the category must be assigned to a filter or NAT rule, or the alias must be referenced by a rule source or destination, and the rule must be saved so the affected tooltip is rendered. Script then executes in the session of an administrator or other user who opens the affected Rules or NAT page. The script can access CSRF material and perform authenticated actions as the victim. This issue is fixed in version 26.1.11."
}
],
"lastModified": "2026-10-20T03:17:16.200",
"sourceIdentifier": "security-advisories@github.com"
}