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 INTMAX, 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

GNU Wget through 1.25.0, fixed in commit 37a40fc, contains a heap buffer underread vulnerability in the cleanmetalinkstring() function within src/metalink.c that allows a malicious server to trigger memory corruption by serving a Metalink document containing a whitespace-only URL. Attackers can cause the function to decrement a pointer past the start of the buffer when processing an all-whitespace Metalink URL, potentially leading to abnormal program behavior.

GNU Wget through 1.25.0, fixed in commit 37a40fc, contains a heap buffer underread vulnerability in the cleanmetalinkstring() function within src/metalink.c that allows a malicious server to trigger memory corruption by serving a Metalink document containing a whitespace-only URL. Attackers can cause the function to decrement a pointer past the start of the buffer when processing an all-whitespace Metalink URL, potentially leading to abnormal program behavior.

GNU Wget through 1.25.0, fixed in commit dd692d9, contains a heap buffer overflow vulnerability in the htmlquotestring() function in src/convert.c that allows a remote attacker to trigger memory corruption by supplying a crafted HTML attribute with a large number of characters requiring entity encoding. A server-supplied HTML attribute causes a signed integer counter to overflow during output size accumulation, resulting in an undersized heap allocation and subsequent heap buffer overflow during the copy phase.

GNU Wget through 1.25.0, fixed in commit dd692d9, contains a heap buffer overflow vulnerability in the htmlquotestring() function in src/convert.c that allows a remote attacker to trigger memory corruption by supplying a crafted HTML attribute with a large number of characters requiring entity encoding. A server-supplied HTML attribute causes a signed integer counter to overflow during output size accumulation, resulting in an undersized heap allocation and subsequent heap buffer overflow during the copy phase.

GNU Wget through 1.25.0, fixed in commit c2640fe, contains a heap buffer overflow vulnerability in the convertfname() function within src/url.c that allows remote attackers to trigger memory corruption through a server-supplied filename requiring character set conversion. When the output buffer is too small during iconv E2BIG reallocation, the reallocation logic miscalculates the remaining space, leading to a heap buffer overflow that can be exploited via a maliciously crafted server response.

GNU Wget through 1.25.0, fixed in commit c2640fe, contains a heap buffer overflow vulnerability in the convertfname() function within src/url.c that allows remote attackers to trigger memory corruption through a server-supplied filename requiring character set conversion. When the output buffer is too small during iconv E2BIG reallocation, the reallocation logic miscalculates the remaining space, leading to a heap buffer overflow that can be exploited via a maliciously crafted server response.

GNU Wget does not validate the IP address provided by an FTP PASV response while operating in FTP passive mode. A malicious FTP server, or an HTTP server that redirects to an FTP URL, can exploit this behavior to redirect Wget’s data connection to an arbitrary IP address and port. This allows an attacker to forge server-side requests (SSRF) from the machine running Wget, potentially accessing localhost services or internal network resources.

GNU Wget through 1.25.0, fixed in commit 43d3ba9, contains an integer overflow vulnerability in the parsecontentrange() function within src/http.c that allows server-controlled values to cause signed integer arithmetic to overflow. Attackers can supply malicious Content-Range header values to trigger undefined behavior and download desynchronization in the affected client.

GNU Wget could allow a remote authenticated attacker to bypass security restrictions, caused by the mishandling of semicolons in the userinfo subcomponent of a URI. By sending a specially crafted request, an attacker could exploit this vulnerability to perform unauthorized actions.

CRLF injection vulnerability in the urlparse function in url.c in Wget through 1.19.1 allows remote attackers to inject arbitrary HTTP headers via CRLF sequences in the host subcomponent of a URL.

wget 1.5.3 follows symlinks to change permissions of the target file instead of the symlink itself.

The ftpsyst function in ftp-basic.c in Free Software Foundation (FSF) GNU wget 1.10.2 allows remote attackers to cause a denial of service (application crash) via a malicious FTP server with a large number of blank 220 responses to the SYST command.

A buffer overflow vulnerability was found in GNU Wget 1.20.1 and earlier. An attacker may be able to cause a denial-of-service (DoS) or may execute an arbitrary code.

References:

https://jvn.jp/en/jp/JVN25261088/

Last updated 25 August 2025

GNU Wget before 1.19.5 is prone to a cookie injection vulnerability in the respnew function in http.c via a \r\n sequence in a continuation line.

Directory traversal vulnerability in wget before 1.8.2-4 allows a remote FTP server to create or overwrite files as the wget user via filenames containing (1) /absolute/path or (2) .. (dot dot) sequences.

Wget 1.9 and 1.9.1 allows local users to overwrite arbitrary files via a symlink attack on the name of the file being downloaded.

wget 1.8.x and 1.9.x allows a remote malicious web server to overwrite certain files via a redirection URL containing a ".." that resolves to the IP address of the malicious server, which bypasses wget's filtering for ".." sequences.

wget 1.8.x and 1.9.x does not filter or quote control characters when displaying HTTP responses to the terminal, which may allow remote malicious web servers to inject terminal escape sequences and execute arbitrary code.