CVE-2020-25900 Overview
CVE-2020-25900 is an information disclosure vulnerability in the HelloTalk language-exchange mobile application through version 3.4.1. The application stores full-precision GPS coordinates for users who intended to share only their country or city. These coordinates were then propagated into a local database on other users' clients, exposing precise location data beyond the user's intent. The client-side database was changed in 2019 to encrypt that stored data. The issue is categorized under [CWE-359] Exposure of Private Personal Information to an Unauthorized Actor.
Critical Impact
Remote actors can obtain full-precision GPS coordinates of HelloTalk users who only consented to country- or city-level location sharing.
Affected Products
- HelloTalk mobile application versions through 3.4.1
- HelloTalk client database storing peer location records (pre-2019 unencrypted form)
- Users sharing only country- or city-level location through the app
Discovery Timeline
- 2026-06-05 - CVE-2020-25900 published to NVD
- 2026-06-05 - Last updated in NVD database
Technical Details for CVE-2020-25900
Vulnerability Analysis
The vulnerability stems from the application transmitting and storing precise GPS coordinates regardless of the user's chosen location-sharing granularity. When a HelloTalk user selects country- or city-level sharing, the application interface implies coarse-grained disclosure. However, the underlying client transmits full-precision latitude and longitude values. These values are persisted in databases on the clients of other users who interact with the affected profile.
An attacker who extracts the local HelloTalk database from their own device can recover the unmodified coordinates of other users. This converts an intended coarse location into a precise geolocation, often accurate to within meters. Refer to the Isopach CVE-2020-25900 Analysis for the original technical writeup.
Root Cause
The root cause is a mismatch between the user-facing privacy setting and the data actually serialized to the wire and to peer-side storage. The application applied location truncation only at the presentation layer rather than at the data layer.
Attack Vector
Exploitation requires no authentication beyond having a HelloTalk account. An attacker installs the application, interacts with target users, and then inspects the local SQLite-style database on their own device. Coordinates of any users surfaced through the app become available. Network-level capture against pre-2019 clients yields the same data without device extraction.
No verified proof-of-concept code is published for this issue. The vulnerability is a logic and data-handling flaw rather than a memory or injection bug, so exploitation does not require crafted payloads.
Detection Methods for CVE-2020-25900
Indicators of Compromise
- Presence of HelloTalk client versions at or below 3.4.1 on managed mobile devices.
- Local HelloTalk database files containing latitude and longitude fields with precision beyond two decimal places for peer records.
- Outbound network traffic from the HelloTalk app carrying high-precision coordinate fields when user privacy is set to country or city.
Detection Strategies
- Inventory mobile devices using mobile device management (MDM) tooling to identify installed HelloTalk versions through 3.4.1.
- Inspect application sandboxes on test devices for HelloTalk databases that retain full-precision coordinates of other users.
- Use mobile traffic inspection to confirm whether the installed client transmits coarsened or full-precision coordinates.
Monitoring Recommendations
- Track HelloTalk version strings reported by enrolled devices and alert on versions at or below 3.4.1.
- Review data loss prevention (DLP) logs for location-bearing payloads exfiltrated from corporate-owned mobile endpoints.
- Monitor user reports of unexpected proximity-based contact, which can indicate location leakage.
How to Mitigate CVE-2020-25900
Immediate Actions Required
- Upgrade HelloTalk on all managed devices to a version newer than 3.4.1.
- Instruct users who relied on country- or city-level sharing to assume prior coordinates were exposed and to review historical privacy expectations.
- Remove HelloTalk from devices that hold sensitive personnel where precise location disclosure poses a safety risk.
Patch Information
The vendor modified the client in 2019 to encrypt the peer-side database that stored coordinates. Users must run a current HelloTalk release to receive the storage-level protection. No vendor advisory URL is included in the NVD record. Consult the Isopach CVE-2020-25900 Analysis for additional context.
Workarounds
- Disable location permissions for HelloTalk in the mobile operating system settings to prevent the app from accessing GPS at all.
- Use the application only on devices with a coarse-location-only permission grant where the OS supports that control.
- Restrict HelloTalk usage on corporate devices through MDM application allowlists until the upgraded version is deployed.
# Example: revoke location permission for HelloTalk on Android via adb
adb shell pm revoke com.hellotalk android.permission.ACCESS_FINE_LOCATION
adb shell pm revoke com.hellotalk android.permission.ACCESS_COARSE_LOCATION
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
