CVE-2026-58391

MEDIUMPre-NVD 5.45.4
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This medium-severity CVE scores 5.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (19th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Trending — 3 sources updated this weekElevated

Also known asEUVD-2026-102113 (ENISA EUVD)Source: ENISA EUVD

5.4EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 5.4Exploit: No code on recordExposed services: Not assessed

The CVE record names the fixed release — apply it.

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.

CVSS v3
5.4
EG Score
5.4MEDIUMmedium confidence
EG Risk
40
EG Risk 40/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity54% × 45%
Impact severity (EG Severity): CVSS 5.4 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: The CVE record names the fixed release. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
19th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (5.4): severity, escalated by confirmed exploitation. This CVE's 5.4 is its impact severity (EG Severity), not escalated.

EG Severity
5.4 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
EG Likelihood
0.3% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

The CVE record names the fixed release. Apply it within your standard update timelines.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

October 15, 2026

Last Modified

October 20, 2026

Advisory Details (4)

Auto-updated Oct 15, 2026
🔬 Proof of concept available. Fix named in the CVE record. Sources: github, github_commit.
Web page🟡 PoC Available

Chasing the OPNsense RCE: The Story Behind My First CVEs (CVE-2026-57155) | HackerAsk

https://hackerask.com/posts/opnsense
GitHub commit

commit fb3b8a07f407 (opnsense/core)

Fix landed in opnsense/core commit fb3b8a07f407 — awaiting tagged release

https://github.com/opnsense/core/commit/fb3b8a07f407ce281b1dde748706acbb0bc514ce
GitHub commit

commit 5e6313f50546 (opnsense/core)

Fix landed in opnsense/core commit 5e6313f50546 — awaiting tagged release

https://github.com/opnsense/core/commit/5e6313f50546474031805039e209830b63b2b0e4
GitHub advisoryMentions a patch (unverified)🟡 PoC Available

Stored XSS in Firewall Rules/NAT pages via a HTML-attribute breakout · Advisory · opnsense/core · GitHub

https://github.com/opnsense/core/security/advisories/GHSA-2xrm-p255-p43h

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 9× in last 7d / 22× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

  1. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  2. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  3. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  4. 2026-10-28 15:25 UTCOSV refresh
  5. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  6. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  7. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  8. 2026-10-25 14:16 UTCEG score recompute
  9. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  10. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  11. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  12. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  13. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  14. 2026-10-20 03:26 UTCEG score recompute
  15. 2026-10-20 02:50 UTCEG score recompute
  16. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  17. 2026-10-18 03:28 UTCEG score recompute
  18. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  19. 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  20. 2026-10-15 16:35 UTCEG score recompute
  21. 2026-10-15 15:23 UTCEG score recomputeFirst assessed: 5.4 MEDIUM
  22. 2026-10-15 15:22 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-58391?
CVE-2026-58391 is a medium-severity vulnerability; its CVE record was published on October 15, 2026. 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 filterrule.volt and natrule.volt without quote-safe encoding. The response layer uses ENT_NOQUOTES, so a…
When was the CVE record for CVE-2026-58391 published?
The CVE record for CVE-2026-58391 was published on October 15, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 20, 2026; the record at its source may have been updated since.
Is CVE-2026-58391 actively exploited?
CVE-2026-58391 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (19th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-58391?
CVE-2026-58391 has a CVSS base score of 5.4 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-58391?
The CVE record for CVE-2026-58391 names the fix: "This issue is fixed in version 26.1.11."

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