Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-08-25T14:17:04 wget: wget: Denial of Service via crafted FTP OPIE/S-KEY authentication challenge 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H CWE-835

GNU wget is vulnerable to denial of service in its FTP OPIE/S-KEY authentication functionality. The server-supplied sequence number from the FTP challenge line is used as an iteration count for an MD5 key-derivation loop without any upper bound validation. A malicious FTP server or a network attacker positioned to intercept FTP traffic can send a crafted OPIE challenge with a sequence number near INT_MAX, causing wget to perform up to approximately 2.1 billion MD5 computations and suspend for some time. The --timeout option does not mitigate this because it applies only to network I/O, not CPU computation. This issue was fixed in commit e9697d98e7249b0f68a6be040a4f3dcc5bc101fa

A flaw was found in wget's FTP OPIE/S-KEY authentication functionality. A malicious FTP server or a network attacker can send a specially crafted OPIE challenge. This challenge contains a sequence number that, when processed by wget, can lead to an excessive number of cryptographic computations. This prolonged computation can cause wget to become unresponsive, resulting in a denial of service.

All versions of wget as shipped with Red Hat Enterprise Linux, Red Hat In-Vehicle Operating System, and Fedora are affected. Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. Red Hat Enterprise Linux 10 Fix deferred wget Red Hat Enterprise Linux 6 Fix deferred wget Red Hat Enterprise Linux 7 Fix deferred wget Red Hat Enterprise Linux 8 Fix deferred wget Red Hat Enterprise Linux 9 Fix deferred wget https://www.cve.org/CVERecord?id=CVE-2026-16599 https://nvd.nist.gov/vuln/detail/CVE-2026-16599 https://cert.pl/en/posts/2026/08/CVE-2026-16599 https://gitlab.com/gnuwget/wget https://gitlab.com/gnuwget/wget/-/commit/e9697d98e7249b0f68a6be040a4f3dcc5bc101fa