CVE-2026-75833: grav Open Redirect (CVSS 4.2)

Description

The Grav API plugin (getgrav/grav-plugin-api, bundled with Grav 2.0's admin-next/API stack) before version 1.0.14 contains an open redirect weakness in SsoController::sanitizeReturnTo(). The function rejects a literal '//' prefix but does not account for browsers normalizing backslashes to slashes in special (http/https) schemes, so a returnTo value such as '/\evil.com' passes the guard and is later resolved by the browser as the protocol-relative URL '//evil.com'. Following a legitimate OAuth login flow, an attacker-supplied returnTo parameter could redirect an authenticated victim to an attacker-controlled site for post-login phishing. Full browser-side exploitability depends on the admin-next SPA's client-side oauth-callback handler and was not independently verified by the reporter.

Metrics

CVSS 3.1

4.2/10

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

CVSS 4.0

8.6/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/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:X

EPSS Probability

0.19%

9.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-601

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
getgrav	grav	< 1.0.14

References

Timeline

Published: Aug 18, 2026
Last Modified: Sep 8, 2026
Status: Deferred

Frequently Asked Questions

What is CVE-2026-75833?

The Grav API plugin (getgrav/grav-plugin-api, bundled with Grav 2.0's admin-next/API stack) before version 1.0.14 contains an open redirect weakness in SsoController::sanitizeReturnTo(). The function rejects a literal '//' prefix but does not account for browsers normalizing backslashes to slashes in special (http/https) schemes, so a returnTo value such as '/\evil.com' passes the guard and is later resolved by the browser as the protocol-relative URL '//evil.com'. Following a legitimate OAuth login flow, an attacker-supplied returnTo parameter could redirect an authenticated victim to an attacker-controlled site for post-login phishing. Full browser-side exploitability depends on the admin-next SPA's client-side oauth-callback handler and was not independently verified by the reporter.

How severe is CVE-2026-75833?

CVE-2026-75833 has a CVSS score of 4.2/10 (MEDIUM severity). The EPSS model estimates a 0.19% probability of exploitation in the next 30 days.

How do I fix CVE-2026-75833?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

How Strix Helps

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