# CVE-2026-128637: Open Redirect in MISP Modules Website Login via Unvalidated next Parameter

Status: published. Published: 2026-11-13. Updated: 2026-11-13.

The MISP Modules website component contains an open redirect vulnerability in its login endpoint. The /login route accepted a user-supplied next query parameter and passed it directly to Flask's redirect() function without validating the destination. An attacker could craft a URL such as https://victim-host/login?next=https://attacker.example/phish and deliver it to a user (e.g., via email or a lookalike page). After the user successfully authenticated, the application issued a 302 redirect to the attacker-controlled external URL. This enables phishing attacks where a user, believing they are still on the legitimate MISP Modules site, may enter additional credentials or sensitive information on the attacker's page. It can also be used to obscure the true destination of a link, bypassing user trust in the legitimate domain. The vulnerability requires the victim to interact with the crafted URL and complete a login, but no prior authentication or special configuration is needed on the attacker's side. The affected component is the website sub-project of misp-modules, specifically the account blueprint in website/app/account/account.py. No version boundaries are specified in the patch metadata.

## Remediation

- fix: The fix introduces a _safe_next_url() validation function that restricts post-login redirect destinations to local paths or same-host HTTP(S) URLs. Any target that is empty, contains backslashes, control characters, leading/trailing whitespace, an unrecognized scheme, a mismatched host, or a protocol-relative form is rejected and the user is redirected to the home page (/). Accepted same-host URLs are normalized to local paths (scheme and authority stripped) while preserving query strings and fragments, ensuring the Location header always contains a relative path. This eliminates the ability to redirect users to arbitrary external destinations after authentication. (source: CNA: CIRCL)
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: CIRCL) — https://github.com/MISP/misp-modules/commit/d115f00414e761b0b70c8c8671edac681de74a4c

## Affected products and versions

- misp / misp-modules: ≥ 0; ≤ 3.1.4 (affected, semver). Source: CNA: CIRCL

## Severity and prioritization

- CVSS 4.0: 5.1 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N; source: CNA: CIRCL

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation none; automatable yes; technical impact partial; source CNA: CIRCL

- Weaknesses: CWE-601

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/MISP/misp-modules/commit/d115f00414e761b0b70c8c8671edac681de74a4c (CNA: CIRCL; patch)

## Provenance

- CNA: CIRCL: https://www.cve.org/CVERecord?id=CVE-2026-128637; retrieved 2026-11-13; source updated 2026-11-13

Revision: 877ed4f0389f162e35f08cdcd274be7ea0939d65de14d85e403ff6126330fd1d

Canonical: https://y2.dev/cve/CVE-2026-128637

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