MISP Dashboard Button Widget Allows Stored XSS via Unsafe javascript: and Backslash URLs

published 2026-09-07 2 mo ago modified 2026-09-09 2 mo ago also EUVD-2026-72372

cvss: 5.4; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 14%
public exploits: 0; none known

Affected versions of MISP insufficiently validate URLs used by dashboard widgets, particularly the Button widget.

The widget's URL is stored configuration controlled by a user. The previous renderer considered a URL safe if it appeared relative or if its parsed hostname matched the configured MISP hostname. That logic failed to reject dangerous schemes and URL forms that browsers normalize differently from PHP's URL parsing.

As a result, values such as javascript: URLs or backslash-based authority forms could reach the generated anchor's href and execute script or navigate to an attacker-controlled origin when another user interacted with the widget. The upstream commit describes the issue as:

“javascript: and backslash URLs reached the href (stored XSS)”.

The fix routes widget URLs through a shared DashboardURLValidator, rejects dangerous schemes, raw backslashes, control characters, and unauthorized absolute origins, and validates the URL both in the widget handler and renderer.

Version affected: ≤2.5.45

Patch / fix

links 1

github.com/MISP/MISP@adf704e commit

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 2 mo ago (2026-09-08)

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	4.0	5.1	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
CNA	4.0	5.1	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD	3.1	5.4	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Affected products

MISP MISP

Classification

Weakness

CWE-79 Improper Neutralization of Input During Web Page Generation
CWE-20 Improper Input Validation

References

github.com /MISP/MISP/commit/adf704e94
patch

Sources

CVE List CVE-2026-86440
NVD CVE-2026-86440

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary