Full Report
Electron packages are signed in order to prevent tampering. Many applications, such as Signal and 1Password, use this. Electron is based on the Chrome browser. V8 heap snapshots occur from a user-writable directory in Chrome. These are used for rendering various browser components from disk instead of doing it over and over again. The bypass for the code integrity is simply done by modifying the V8 snapshots on the system. By clobbering Array.isArray() in JavaScript, the author can easily trigger a crash. Naturally, this hijacking of functions and be used to add arbitrary code and circumvent all integrity checks. This vulnerability is super simple but requires a deep knowledge of Chrome. Understanding something popular very well can lead to seemingly simple security issues with devastating consequences, such as this one.
Analysis Summary
# Vulnerability: Chromium-Based V8 Heap Snapshot Integrity Bypass
## CVE Details
- **CVE ID:** CVE-2025-55305
- **CVSS Score:** Not yet finalized (Estimated: Medium–High)
- **CWE:** CWE-353 (Missing Support for Integrity Check) / CWE-345 (Insufficient Verification of Data Authenticity)
## Affected Systems
- **Products:** Electron-based applications and Chromium-based browsers.
- **Versions:**
- 1Password (Versions prior to v8.11.8-40)
- Signal (Affected prior to maintainer patches)
- Slack (Affected prior to maintainer patches)
- Google Chrome and other Chromium derivatives.
- Electron framework (Versions prior to the CVE-2025-55305 fix).
- **Configurations:** Applications installed in user-writable directories (e.g., `%AppData%\Local` on Windows or `/Applications` on macOS without root ownership) are particularly vulnerable to local persistent backdooring.
## Vulnerability Description
Electron and Chromium applications use **V8 heap snapshots** to accelerate the initialization of JavaScript environments (isolates). These snapshots are deserialized into memory to provide a "warm" start for the browser engine.
The vulnerability stems from an inconsistency in how integrity fuses (specifically `EnableEmbeddedAsarIntegrityValidation`) were implemented. While Electron can verify the integrity of application archives (ASAR files), it failed to verify the integrity of the V8 heap snapshot files stored on disk. Because these files reside in user-writable directories, an attacker can modify the snapshot to "clobber" (overwrite) JavaScript built-ins. For example, by modifying `Array.isArray()`, an attacker can redirect execution flow to arbitrary, unsigned malicious code that executes within the context of the trusted, signed application.
## Exploitation
- **Status:** PoC available (Technique documented by Trail of Bits); evidence of similar techniques being used in the wild (e.g., Loki C2).
- **Complexity:** Medium (Requires deep knowledge of Chrome/V8 internals to craft snapshots).
- **Attack Vector:** Local (Requires the ability to write to the application's directory, typically achieved via initial malware infection or local access).
## Impact
- **Confidentiality:** High (Malicious code can access application data, secrets, and user input).
- **Integrity:** Total (Bypasses code signing and integrity fuses, allowing arbitrary backdoors).
- **Availability:** High (Modified snapshots can be used to cause consistent application crashes).
## Remediation
### Patches
- **1Password:** Update to version **v8.11.8-40** or higher.
- **Electron Framework:** Update to the latest stable version containing the fix for **CVE-2025-55305**, which extends integrity checks to include heap snapshots.
- **Other Apps:** Ensure Signal, Slack, and Chrome-based browsers are updated to the latest available versions.
### Workarounds
- **Permissions:** Relocate application installations to directories requiring Administrative/Root privileges to modify (e.g., `C:\Program Files` or root-owned `/Applications`).
- **EDR:** Monitor for unexpected modifications to `.bin` or snapshot files within application folders.
## Detection
- **Indicators of Compromise:** Unexpected changes to V8 snapshot files (often named `v8_context_snapshot.bin` or similar) where the file hash does not match the original distribution.
- **Detection Methods:**
- File integrity monitoring (FIM) on application installation directories.
- Application Whitelisting tools that validate all loaded components beyond just the primary executable.
## References
- **Trail of Bits Advisory:** hxxps://blog[.]trailofbits[.]com/2025/09/03/subverting-code-integrity-checks-to-locally-backdoor-signal-1password-slack-and-more/
- **Electron Security:** hxxps://www[.]electronjs[.]org/docs/latest/tutorial/fuses
- **MITRE ATT&CK T1218.015:** hxxps://attack[.]mitre[.]org/techniques/T1218/015/