Saltcorn: Open Redirect in `POST /auth/login` due to incomplete `is_relative_url` validation (backslash bypass)

Description

Saltcorn validates the post-login dest parameter with a string check that only blocks :/ and //. Because all WHATWG-compliant browsers normalise backslashes (\) to forward slashes (/) for special schemes, a payload such as /\evil.com/path slips through is_relative_url(), is emitted unchanged in the HTTP Location header, and causes the browser to navigate cross-origin to an attacker-controlled domain.

Recommendation

Update the @saltcorn/server package to the latest compatible version. Followings are version details:

• Affected version(s): **>= 1.6.0-alpha.0, < 1.6.0-beta.5

  >= 1.5.0-beta.0, < 1.5.6

  < 1.4.6**

• Patched version(s): **1.6.0-beta.5

  1.5.6

  1.4.6**

References

• GHSA-f3g8-9xv5-77gv
• CVE-2026-42259
• CWE-601
• CAPEC-310
• OWASP 2021-A1
• OWASP 2021-A6

Related Issues

• Parse Server has an auth provider validation bypass on login via partial authData - CVE-2026-33409
• @langchain/community affected by SSRF Bypass in RecursiveUrlLoader via insufficient URL origin validation - CVE-2026-26019
• Feathers has an open redirect in OAuth callback enables account takeover - CVE-2026-27191
• Neotoma: Unauthenticated Inspector/API access via reverse-proxy loopback auth bypass - CVE-2026-45577

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Tags:

npm

@saltcorn/server