W3 maintains a modestly represented portfolio of web standards reference implementations and validators—including the Amaya browser, CSS Validator, and EPUB checking tools—that collectively serve as conformance and parsing infrastructure across the web platform ecosystem. The vulnerability exposure centers on input-handling and parsing logic, recurring through cross-site scripting, buffer boundary issues, XML external entity references, and infinite-loop conditions endemic to validators and document processors. Public exploit code has frequently been made available for this vendor's vulnerabilities, consistent with the accessibility and tooling nature of these reference implementations; live severity, exploitation, and exposure counts are shown alongside this summary.
The number and severity of CVEs published that impact products developed by W3 over time
Signals from CVEs in this vendor scope (8 CVEs).
8 CVEs · Highest risk first
| CVE | Published | CVSS | Risk | KEV | Exploit |
|---|---|---|---|---|---|
CVE-2009-0323HIGH Multiple stack-based buffer overflows in W3C Amaya Web Browser 10.0 and 11.0 allow remote attackers to execute arbitrary code via (1) a long type parameter in an input tag, which i | Jan 28, 2009 | 10.0 | 78 | NO | YES |
CVE-2009-1209HIGH Stack-based buffer overflow in W3C Amaya Web Browser 11.1 allows remote attackers to execute arbitrary code via a script tag with a long defer attribute. | Apr 1, 2009 | 9.3 | 40 | NO | YES |
CVE-2025-1781MEDIUM There is a XXE in W3CSS Validator versions before cssval-20250226 that allows an attacker to use specially-crafted XML objects to coerce server-side request forgery (SSRF). This c | Mar 28, 2025 | 6.5 | 20 | NO | NO |
CVE-2023-30300MEDIUM An issue in the component hang.wasm of WebAssembly 1.0 causes an infinite loop. | May 3, 2023 | 5.5 | 20 | NO | NO |
CVE-2016-9487HIGH EpubCheck 4.0.1 does not properly restrict resolving external entities when parsing XML in EPUB files during validation. An attacker who supplies a specially crafted EPUB file may | Jul 13, 2018 | 7.8 | 20 | NO | NO |
CVE-2014-125108MEDIUM A vulnerability was found in w3c online-spellchecker-py up to 20140130. It has been rated as problematic. This issue affects some unknown processing of the file spellchecker. The m | Dec 23, 2023 | 6.1 | 18 | NO | NO |
CVE-2021-4296MEDIUM A vulnerability, which was classified as problematic, has been found in w3c Unicorn. This issue affects the function ValidatorNuMessage of the file src/org/w3c/unicorn/response/imp | Dec 29, 2022 | 6.1 | 18 | NO | NO |
The W3C High Resolution Time API, as implemented in various web browsers, does not consider that memory-reference times can be measured by a performance.now "Time to Tick" approach | Feb 27, 2017 | 3.7 | 13 | NO | NO |
Signals from CVEs in this vendor scope (8 CVEs).
An overview of all social media posts that mention a CVE ID that affects a product developed by W3.
Media articles that mention a CVE ID that affects a product developed by W3 — matched by CVE ID, not by vendor name.