Google Chrome 127.x/128.x AppBound Cookie Encryption information exposure

Summaryinfo

A vulnerability has been found in Google Chrome 127.x/128.x and classified as problematic. This impacts an unknown function of the component AppBound Cookie Encryption. This manipulation causes information exposure. This vulnerability appears as CVE-2025-34091. The attack may be initiated remotely. There is no available exploit. The affected component should be upgraded.

Detailsinfo

A vulnerability has been found in Google Chrome 127.x/128.x and classified as problematic. Affected by this vulnerability is an unknown part of the component AppBound Cookie Encryption. The manipulation with an unknown input leads to a information exposure vulnerability. The CWE definition for the vulnerability is CWE-203. The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor, which exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not. As an impact it is known to affect confidentiality. The summary by CVE is:

A padding oracle vulnerability exists in Google Chrome’s AppBound cookie encryption mechanism due to observable decryption failure behavior in Windows Event Logs when handling malformed ciphertext in SYSTEM-DPAPI-encrypted blobs. A local attacker can repeatedly send malformed ciphertexts to the Chrome elevation service and distinguish between padding and MAC errors, enabling a padding oracle attack. This allows partial decryption of the SYSTEM-DPAPI layer and eventual recovery of the user-DPAPI encrypted cookie key, which is trivially decrypted by the attacker’s own context. This issue undermines the core purpose of AppBound Encryption by enabling low-privileged cookie theft through cryptographic misuse and verbose error feedback. Confirmed in Google Chrome with AppBound Encryption enabled. Other Chromium-based browsers may be affected if they implement similar COM-based encryption mechanisms. This behavior arises from a combination of Chrome’s AppBound implementation and the way Microsoft Windows DPAPI reports decryption failures via Event Logs. As such, the vulnerability relies on cryptographic behavior and error visibility in all supported versions of Windows.

The weakness was presented by Ari Novick. The advisory is shared at cyberark.com. This vulnerability is known as CVE-2025-34091 since 04/15/2025. The exploitation appears to be difficult. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 07/03/2025). MITRE ATT&CK project uses the attack technique T1592 for this issue.

Upgrading to version 129 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2025-19758). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Web Browser

Vendor

• Google

Name

• Chrome

Version

• 127.x
• 128.x

License

• free

Website

• Vendor: https://www.google.com/
• Product: https://www.google.com/chrome/

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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