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AndroidOperating system · Google

CVE-2013-4787

HIGH · 9.3 CVSS v2.0 Published 2013-07-09
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
High EPSS Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Android 1.6 Donut through 4.2 Jelly Bean does not properly check cryptographic signatures for applications, which allows attackers to execute arbitrary code via an application package file (APK) that is modified in a way that does not violate the cryptographic signature, probably involving multiple entries in a Zip file with the same name in which one entry is validated but the other entry is installed, aka Android security bug 8219321 and the "Master Key" vulnerability.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A signature verification bypass vulnerability in Android's package installer allows attackers to modify APK files without breaking the cryptographic signature. The flaw occurs when multiple Zip file entries share the same filename - one entry passes signature validation while a different (malicious) entry gets installed. This enables arbitrary code execution through seemingly legitimate apps.

MitigationApply the Android security patch for CVE-2013-4787 (or upgrade to Android 4.3+) to device fleets; for custom Android implementations, fix the PackageManagerService signature verification to validate ALL entries with duplicate names, not just the first one encountered.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
AndroidOperating system
Affected:= 1.6= 2.0= 2.0.1= 2.1= 2.2= 2.2.1= 2.2.2= 2.2.3= 2.3= 2.3.1= 2.3.2= 2.3.3

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
M
Authentication
None
Confidentiality
Complete
Integrity
Complete
Availability
Complete

AV:N/AC:M/Au:N/C:C/I:C/A:C

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check the Android OS version
    On the device, go to Settings > About Phone (or About Device) > Android version. Alternatively, use 'adb shell getprop ro.build.version.release'
    Affected if The version is 1.6, 2.0, 2.0.1, 2.1, 2.2, 2.2.1, 2.2.2, 2.2.3, 2.3, 2.3.1, 2.3.2, or 2.3.3
  2. Verify the package installer implementation
    If using a custom Android build, inspect the PackageManagerService source code (typically in frameworks/base/services/java/com/android/server/pm/) and locate the signature verification logic for APK installation
    Affected if The installer validates signatures only on the first ZIP entry encountered for each filename, rather than validating all entries with duplicate names
  3. Test an APK for duplicate ZIP entries
    Use a ZIP tool (like 'unzip -l' or 7-Zip) to list entries in an APK file and look for multiple entries sharing the same filename
    Affected if The APK contains duplicate filename entries and the device runs an affected Android version

If the Android version is 2.3.3 or earlier, or if the custom package manager only validates the first of duplicate-named ZIP entries, the environment is vulnerable to CVE-2013-4787.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the Android security patch for CVE-2013-4787 (or upgrade to Android 4.3+) to device fleets; for custom Android implementations, fix the PackageManagerService signature verification to validate ALL entries with duplicate names, not just the first one encountered.

Recommended fix Moderate confidence

Android 4.3 (Jelly Bean) or later

  1. 1. Backup all important data from the device to a secure location
  2. 2. Verify that the device hardware is supported for a newer Android version
  3. 3. Check if the device manufacturer provides an official OTA update to Android 4.3 or later
  4. 4. If official updates are unavailable, consider installing a custom ROM (such as CyanogenMod) that includes the security patch for this vulnerability
  5. 5. After upgrading, verify the Android version is 4.3 (Jelly Bean) or higher to confirm the vulnerability is patched
  6. 6. Reinstall applications only from trusted sources like Google Play Store
Caveat Custom ROMs may void warranty, require bootloader unlocking, and may not receive future official updates

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Android Scoped from the published advisory
  • Consultation8.0 h
  • Implementation24.0 h
  • Testing16.0 h
  • Review / QA8.0 h
56.0 hours of engineering $9,760
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2013-4787 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data