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CGI implementation in Yaws web server versions 1.81 to 2.0.7 is vulnerable to OS command injection.
Last updated 26 August 2025
yawsconfig.erl in Yaws through 2.0.2 and/or 2.0.7 loads obsolete TLS ciphers, as demonstrated by ones that allow Sweet32 attacks, if running on an Erlang/OTP virtual machine with a version less than 21.0.
yaws before 2.0.4 does not attempt to address RFC 3875 section 4.1.18 namespace conflicts and therefore does not protect CGI applications from the presence of untrusted client data in the HTTPPROXY environment variable, which might allow remote attackers to redirect a CGI application's outbound HTTP traffic to an arbitrary proxy server via a crafted Proxy header in an HTTP request, aka an "httpoxy" issue.
Yaws 1.91 has a directory traversal vulnerability in the way certain URLs are processed. A remote authenticated user could use this flaw to obtain content of arbitrary local files via specially-crafted URL request.
Yaws 1.91 allows Unauthenticated Remote File Disclosure via HTTP Directory Traversal with /%5C../ to port 8080. NOTE: this CVE is only about use of an initial /%5C sequence to defeat traversal protection mechanisms; the initial /%5C sequence was apparently not discussed in earlier research on this product.
Multiple cross-site scripting (XSS) vulnerabilities in the wiki application in Yaws 1.88 allow remote attackers to inject arbitrary web script or HTML via (1) the tag parameter to editTag.yaws, (2) the index parameter to showOldPage.yaws, (3) the node parameter to allRefsToMe.yaws, or (4) the text parameter to editPage.yaws.
Directory traversal vulnerability in Yaws 1.89 allows remote attackers to read arbitrary files via ..\ (dot dot backslash) and other sequences.
Yaws 1.85 writes data to a log file without sanitizing non-printable characters, which might allow remote attackers to modify a window's title, or possibly execute arbitrary commands or overwrite files, via an HTTP request containing an escape sequence for a terminal emulator.
Yaws before 1.80 allows remote attackers to cause a denial of service (memory consumption and crash) via a request with a large number of headers.
Yaws Webserver 1.55 and earlier allows remote attackers to obtain the source code for yaws scripts via a request to a yaw script with a trailing %00 (null).