EUVD-2026-34262
GHSA-rx96-8w86-5hhh
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/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:Green
Primary rating from Vendor (CIRCL) · only source for this CVE.
CVSS VectorVendor: CIRCL
Lifecycle Timeline
4DescriptionCVE.org
A URL validation flaw in the MISP dashboard button widget allowed a crafted relative-looking URL to be accepted as a local path while being interpreted by browsers as an external URL. The validation rejected URLs containing an explicit scheme, host, or user component, but did not reject paths beginning with a slash followed by a backslash, such as /\example.com. Some browsers normalize backslashes in URLs as forward slashes, which can turn this into a scheme-relative external navigation target. In addition, the generated href concatenated the reconstructed URL with the original URL, increasing the possibility of unsafe or malformed link generation.
An attacker able to configure or influence a dashboard button URL could craft a button that appears to point inside the application but redirects users to an attacker-controlled site when clicked. This could be used for phishing, credential theft, or social engineering. The patch fixes the issue by rejecting empty paths and paths starting with /\, and by emitting only the reconstructed validated URL in the anchor href.
AnalysisAI
Open redirect in MISP's dashboard button widget (versions up to and including 2.5.38) enables an authenticated, high-privileged user who controls dashboard configuration to plant a crafted button URL that appears to point internally but redirects clicking users to an attacker-controlled external site. The root cause is an incomplete URL allowlist in Button.ctp that blocked explicit schemes, hosts, and user components but did not reject paths beginning with /\ - a pattern several browsers normalize into a scheme-relative URL (i.e., //attacker.com). No public exploit exists and CISA SSVC rates exploitation as none; risk is substantially constrained by the PR:H requirement and the need for a victim to interact with the planted button.
Technical ContextAI
MISP (Malware Information Sharing Platform) is an open-source threat intelligence sharing platform maintained by CIRCL. The vulnerable component is Button.ctp, a PHP CakePHP view element that renders configurable dashboard button widgets. URL validation used PHP's parse_url() to reject components such as host, scheme, and user - but parse_url() does not flag paths like /\example.com as malicious; the path component simply reads as /\example.com with no host extracted. Browsers including Chrome and Edge normalize backslashes within URL paths as forward slashes, transforming /\example.com into //example.com, which is a scheme-relative reference resolved against the current protocol and treated as an absolute external navigation. An additional defect concatenated the reconstructed betterUrl with the original $url in the href, further increasing the risk of malformed or unsafe link generation. CWE-601 (URL Redirection to Untrusted Site, 'Open Redirect') is the root cause class, representing a failure to fully validate the destination of a generated hyperlink before rendering it. The affected CPE is cpe:2.3:a:misp:misp:*:*:*:*:*:*:*:*.
RemediationAI
The upstream fix is available in MISP commit f879f16fb5db7a9aab0a70fdcafea12ce4847e9a, which modifies Button.ctp to reject empty paths and any path whose second character is a backslash, and also removes the double-concatenation of betterUrl and $url in the anchor href. Operators should upgrade to a MISP release incorporating this commit - the fix targets versions beyond 2.5.38, but a specific released patch version was not independently confirmed from the available references; verify the exact release tag in the MISP changelog at https://github.com/MISP/MISP/commit/f879f16fb5db7a9aab0a70fdcafea12ce4847e9a. As an interim compensating control for organizations that cannot patch immediately, restrict dashboard widget configuration permissions to the minimum set of trusted administrators, reducing the attacker's ability to plant crafted URLs. Note that this control does not eliminate the vulnerability if administrative accounts are compromised. Audit existing dashboard button widgets for URLs beginning with /\ as a detection measure.
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