Executive Summary

CVE-2019-25544 is a denial of service vulnerability in Pidgin version 2.13.0 and earlier. It occurs when a local attacker provides an excessively long username string—specifically a buffer of 1000 characters—during account creation. This malformed username causes the application to crash when the user attempts to join a chat, making the application unavailable.

The vulnerability is classified under CWE-807, which relates to reliance on untrusted inputs in a security decision.

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Impact Analysis

This vulnerability can impact you by causing the Pidgin application to crash and become unavailable. Since the crash is triggered by providing an excessively long username during account creation, a local attacker can exploit this to cause a denial of service, disrupting your ability to use the chat client.

The impact is specifically on availability, meaning the application stops functioning properly, which can interrupt communication and productivity.

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Compliance Impact

I don't know

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Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability can be detected by attempting to reproduce the crash condition on Pidgin 2.13.0 by providing an excessively long username string during account creation.'}, {'type': 'paragraph', 'content': 'A practical detection method involves using the provided proof-of-concept exploit which generates a username buffer of 1000 characters.'}, {'type': 'list_item', 'content': "Run the Python script `pidgin.py` to generate a file `pidgin.txt` containing 1000 'A' characters."}, {'type': 'list_item', 'content': 'Open Pidgin, navigate to "Accounts" > "Manage Accounts," and add a new account.'}, {'type': 'list_item', 'content': 'Paste the content of `pidgin.txt` into the "Username" field and enter any string (e.g., "1234") in the "Password" field.'}, {'type': 'list_item', 'content': 'After adding the account, right-click the Pidgin icon in the taskbar\'s hidden icons area, select "Join Chat...", and click "Join."'}, {'type': 'paragraph', 'content': 'If Pidgin crashes during this process, the vulnerability is present on the system.'}] [2]

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Mitigation Strategies

Immediate mitigation steps include preventing local attackers from providing excessively long usernames during account creation in Pidgin 2.13.0.

• Restrict local user access to the Pidgin application to trusted users only.
• Monitor and limit input validation on username fields to reject overly long strings.
• Consider upgrading to a patched version of Pidgin if available or applying any vendor-supplied patches.

Since the vulnerability requires local access and is triggered by malformed input, controlling user permissions and input validation are key immediate defenses.

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