{"answers":{"affected":"","exploited":"There is no known exploitation of CVE-2026-50571 in the wild and no public exploit code.","fix":"No fix has been published for CVE-2026-50571 yet. Limit exposure of the affected software until one is available.","what":"CVE-2026-50571 is a medium-severity vulnerability in w3c websub, published on 27 Oct 2026."},"fix_prompt":"Check this codebase for CVE-2026-50571 and fix it if it is affected.\n\nWhat it is: CVE-2026-50571 is a medium-severity vulnerability in w3c websub, published on 27 Oct 2026. \nExploitation: There is no known exploitation of CVE-2026-50571 in the wild and no public exploit code.\n\nAffected product: w3c websub. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-50571/ (Markdown: https://insights.sbomify.com/CVE-2026-50571/index.md)","id":"CVE-2026-50571","markdown":"https://insights.sbomify.com/CVE-2026-50571/index.md","name":"CVE-2026-50571","record":{"aliases":["GHSA-f4hw-w632-m6wh"],"analysis":null,"analysis_generated_by":null,"assigner":"GitHub_M","cpe":[],"cvss":{"score":5.7,"severity":"medium","source":"cna","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:H/A:N","version":"3.1"},"cwes":[{"id":"CWE-79","name":"Improper Neutralization of Input During Web Page Generation"}],"description":"WebSub is a W3C recommendation produced by the Social Web Working Group. In recommendation REC-websub-20180123, the intent-verification protocol requires a subscriber to echo the `hub.challenge` value, also exposed as `hub_challenge` by some frameworks, but does not require safe response media typing or disabled MIME sniffing. An attacker can initiate a subscription to obtain a callback URL and redirect a victim browser to a crafted verification request containing HTML or JavaScript. Subscribers that return the challenge as `text/html` can execute the reflected content in the subscriber origin, using a victim's existing session to read private data or perform actions, exposing `localStorage` or `sessionStorage` and browser permissions granted to that origin. An alternative uses the verification response as an attacker-controlled same-origin script resource to bypass `script-src 'self'`; this can remain possible with `application/octet-stream` when MIME sniffing is allowed. Safe media typing and `X-Content-Type-Options: nosniff` are both needed to address the described scenarios. WebSub Rocks demonstrated reflection, but the advisory does not establish practical impact on that demonstration site.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":false,"headline":"WebSub: Reflected script execution through intent-verification challenges","id":"CVE-2026-50571","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":null,"year":"2026"},"n_packages":0,"n_references":2,"next":{"headline":"Envoy: ext_authz - RawHttpClientImpl onSuccess 0x0 segfault","id":"CVE-2026-50572"},"packages":[],"prev":{"headline":"Fission: Incomplete capability denylist in Environment/Function PodSpec validation allows tenant-added CAP_SYS_TIME and cross-tenant node wall-clock corruption","id":"CVE-2026-50570"},"products":["websub"],"published":"2026-10-27","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-10-28","vendors":["w3c"]},"summary":null,"url":"https://insights.sbomify.com/CVE-2026-50571/"}