CVE-2025-57821Network attack vector

Cross-origin redirection via malformed URL validation

Published Aug 27, 2025 · Updated Aug 27, 2025

Open redirect in Basecamp google_sign_in before 1.3.0 allows remote attackers to redirect users to another origin after authentication. RedirectProtector.ensure_same_origin accepts a malformed proceed_to value when it fails the qualified-URL test, rather than rejecting every value that is neither a same-origin URL nor an absolute path. Exploitation requires user interaction, cookie-backed Rails flash data, and a separate ability to inject the crafted value; database-backed sessions have no known vector.

CVSS severity4.2
Medium
EPSS probability0.24%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Open redirect in Basecamp google_sign_in before 1.3.0 allows remote attackers to redirect users to another origin after authentication. RedirectProtector.ensure_same_origin accepts a malformed proceed_to value when it fails the qualified-URL test, rather than rejecting every value that is neither a same-origin URL nor an absolute path. Exploitation requires user interaction, cookie-backed Rails flash data, and a separate ability to inject the crafted value; database-backed sessions have no known vector.

The record

CVE
CVE-2025-57821
Published
Aug 27, 2025
Updated
Aug 27, 2025
Vendor
Google
Product
google_sign_in
Classifications
CWE-601, CAPEC-178
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 27, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 27, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Google · google_sign_inversion=< 1.3.0

Published CVSS scores

4.2GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 11, 2026Sep 17, 2026
Latest reporting daySep 17, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-601URL Redirection to Untrusted Site ('Open Redirect')
CAPEC-178Cross-Site Flashing

Public exploit references

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Technologies

Your stack

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Your stack

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