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Cross-site Scripting (XSS)Weakness · CWE-79

CVE-2026-49131

MEDIUM · 5.4 CVSS v3.1 Published 2026-08-03
No fix yet
No fix has been published. The vendor has not shipped a fixed release or patch. You remain exposed.
See remediation →
58/100
Remediation priority · Elevated
Remotely reachable 2 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
OPNsense before 26.1.9 contains a stored cross-site scripting vulnerability that allows authenticated attackers with firewall rule management privileges to inject arbitrary HTML or JavaScript by embedding payloads in the firewall rule description field via the filter API endpoint. The unsanitized description value is persisted and later rendered through the default cell formatter in opnsense_bootgrid.js, which assigns raw cell content to innerHTML, causing injected scripts to execute in the browser of any authenticated user who views the Firewall Rules page, enabling session hijacking or credential theft.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-79

Untrusted input is placed into a web page without being neutralised, so an attacker's markup or script executes in another user's browser. That can hijack sessions, capture keystrokes, or silently perform actions as the victim. Fixing it properly means context-aware output encoding everywhere data meets HTML, backed by a content-security policy as a second line of defence.

General guidance for the cross-site scripting (xss) class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Recommended fix High confidence

OPNsense 26.1.9 or later

  1. 1. Backup your OPNsense configuration before performing any upgrade
  2. 2. Navigate to System > Firmware > Settings in the OPNsense web interface
  3. 3. Check the current firmware version under System > Firmware > Dashboard
  4. 4. Ensure you are running OPNsense 26.1.9 or later by going to System > Firmware > Check for Updates
  5. 5. If an update is available, proceed with the standard upgrade process via System > Firmware > GUI Upgrade or console using 'opnsense-update -f'
  6. 6. After upgrade, verify the version is 26.1.9 or newer
  7. 7. Clear browser cache to ensure the updated opnsense_bootgrid.js is loaded
  8. 8. Verify the fix by creating a test firewall rule with a description containing HTML/script content and confirm it is properly escaped when rendered
Caveat Review OPNsense 26.1.9 release notes for any changes to firewall rule handling or API behavior before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

No vendor fix exists The vendor has not published a patch for this.

There is no version to upgrade to and no patch to apply. Every affected install stays exposed until the vendor ships a fix — or somebody else builds one.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-49131 in production — separate from our analysis above.

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What this is

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