CVE-2026-33209 is a medium-severity cross-site scripting (XSS) vulnerability in avo (rubygems), affecting versions <= 3.30.2. It is fixed in 3.30.3.
Description A reflected cross-site scripting (XSS) vulnerability exists in the return_to query parameter used in the avo interface. An attacker can craft a malicious URL that injects arbitrary JavaScript, which is executed when he clicks a dynamically generated navigation button. Impact This vulnerability may allow execution of arbitrary JavaScript in the context of the application. Impact varies depending on deployment: In unauthenticated setups: exploitable via crafted links sent to users In authenticated setups: limited to authenticated users and requires interaction
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
rubygems
avo (<= 3.30.2)avo → 3.30.3 (rubygems)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter instead of chasing every advisory.
Kodem's runtime-powered SCA identifies whether CVE-2026-33209 is reachable in your applications. Explore open-source security for your team.
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Already deployed Kodem? See CVE-2026-33209 in your environment →Upgrade avo to 3.30.3 or later to resolve this vulnerability.
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CVE-2026-33209 is a medium-severity cross-site scripting (XSS) vulnerability in avo (rubygems), affecting versions <= 3.30.2. It is fixed in 3.30.3. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
avo (rubygems) versions <= 3.30.2 is affected.
Yes. CVE-2026-33209 is fixed in 3.30.3. Upgrade to this version or later.
Whether CVE-2026-33209 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade avo to 3.30.3 or later.