• Platform: Android
• Weakness: MASWE-0027
• Weakness in the numbering of the MASWE beta: MASWE-0052
• Profiles: L1 (basic security), L2 (advanced security)
• Type: static, code, manual
• Knowledge: MASTG-KNOW-0010
• Best practices: MASTG-BEST-0021

Overview

This test evaluates whether an Android app uses checkServerTrusted(...) in an unsafe manner as part of a custom TrustManager, causing any connection configured to use that TrustManager to skip certificate validation.

Such unsafe implementations can allow an attacker to run a [MITM attack](../../../Document/0x04f-Testing-Network-Communication.md#intercepting-network-traffic-through-mitm) with a valid (or self-signed) certificate and intercept or tamper with the app's traffic.

Steps

1. Use MASTG-TECH-0013 to reverse engineer the app.
2. Use MASTG-TECH-0014 to look for the relevant APIs.

Observation

The output should contain a list of locations where checkServerTrusted(...) is used.

Evaluation

The test case fails if checkServerTrusted(...) is implemented in a custom X509TrustManager and does not properly validate server certificates.

Further Validation Required:

Inspect each reported code location using MASTG-TECH-0023, looking for cases such as:

• **Using checkServerTrusted(...) which is error prone, when NSC would be enough.
• Trust manager that does nothing: overriding checkServerTrusted(...) to accept all certificates without any validation, for example by returning immediately without verifying the certificate chain or by always returning true.
• Ignoring errors: failing to throw proper exceptions (e.g. CertificateException or IllegalArgumentException) on validation failure, or catching and suppressing them.
• Using checkValidity()) instead of full validation: relying only on checkValidity() checks whether the certificate is expired or not yet valid, but does not verify trust or hostname matching.
• Explicitly loosening trust: disabling trust checks to accept self-signed or untrusted certificates for convenience during development or testing.
• Misusing getAcceptedIssuers()): Returning null or an empty array without proper handling may effectively disable issuer validation.

Linked Issues

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  • OWASP Application Security Verification Standard (ASVS) 5.0.0, Mai 2025, aus OWASP/ASVS: © 2008-2025 The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Änderungen: in Abschnitte aufgeteilt und in das GRCA-Format umgewandelt, der Wortlaut unverändert. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
  • OWASP Mobile Application Security Verification Standard (MASVS) v2.1.0, Januar 2024, aus OWASP/masvs: © The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
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  • OWASP Mobile Application Security Testing Guide (MASTG) v2.0.0, Juni 2026, aus OWASP/mastg: © The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Nur die Tests und Best Practices, ohne Codebeispiele, Bilder, Werkzeuge und Apps. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert; Verweise auf andere Seiten des MASTG als Links zu mas.owasp.org; die Schwachstelle jedes Tests in der Nummerierung der MASWE v1 und mit ihr verknüpft. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
  • OWASP Software Assurance Maturity Model (SAMM) v2.2.0, Juli 2026, aus owaspsamm/core: © The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert; Kürzel (G-SM-1-A) aus dem Modell gebildet, die Assessment-Fragen als Prüfverfahren ihrer Aktivitäten. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
  • OWASP Top 10:2025, aus OWASP/Top10: © 2003-2025 The OWASP® Foundation, Inc., lizenziert unter CC BY-SA 4.0. Die zehn Kategorien, ohne die Symbole. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0. Die Namen der zugeordneten CWEs (Common Weakness Enumeration): © 2006–2026 The MITRE Corporation. MITRE erlaubt die Nutzung für Forschung, Entwicklung und kommerzielle Zwecke, wenn jede Kopie den Urheberrechtsvermerk und die Lizenz enthält; maßgeblich ist der englische Wortlaut der Lizenz oben und die CWE Terms of Use. CWE™ ist eine Marke der MITRE Corporation.