Moderate Vulnerability in Fetchmail: Stack-Based Buffer Overflow in NTLM Authentication
Summary
ALSA-2026:85959: Moderate: fetchmail security update. Affects fetchmail versions < 6.4.38-3.el10_2.1. Fixed in 6.4.38-3.el10_2.1. How to fix ↓
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Background
Fetchmail is a remote mail retrieval and forwarding utility designed for use over on-demand TCP/IP links, such as SLIP or PPP connections. It supports various remote-mail protocols, including POP2, POP3, RPOP, APOP, KPOP, all IMAPs, ESMTP ETRN, IPv6, and IPSEC. Fetchmail retrieves emails from remote servers and forwards them via SMTP to the user's preferred mail client. This utility is widely used for its versatility and compatibility with numerous email protocols.
Vulnerability Detail
The vulnerability in Fetchmail arises from a stack-based buffer overflow during NTLM authentication, identified as CVE-2026-94184. This flaw could allow an attacker to execute arbitrary code on the affected system, potentially leading to unauthorized access or data compromise. The issue stems from improper handling of input data, which can overflow the buffer and overwrite adjacent memory, creating a security risk.
How To Fix
Minimum fixed version
6.4.38-3.el10_2.1
This is the first release that contains the fix.
sudo dnf update fetchmailTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, users are advised to disable NTLM authentication in Fetchmail configurations until the package can be updated. This can be done by modifying the Fetchmail configuration file to avoid using NTLM for authentication.
Conclusion
The Fetchmail utility has a moderate vulnerability related to a stack-based buffer overflow in NTLM authentication. It is crucial for users to update to the latest version to mitigate risks associated with this vulnerability. Regular monitoring and updates are essential for maintaining security in open-source software.
See every vulnerability recorded for fetchmail →
FAQ
Fetchmail is a utility for retrieving and forwarding emails from remote servers to a local mail client over TCP/IP connections.
CVE-2026-94184 is a stack-based buffer overflow vulnerability in Fetchmail's NTLM authentication process, which could allow attackers to execute arbitrary code.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without any signup.
The risks include potential unauthorized access to the system and data compromise due to arbitrary code execution.
You can update Fetchmail by running 'sudo dnf update fetchmail' in your terminal to ensure you have the latest patched version.
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