{"answers":{"affected":"It affects 1 product.","exploited":"It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73321 exists.","fix":"No fix has been published for CVE-2026-73321 yet. Limit exposure of the affected software until one is available.","what":"CVE-2026-73321 is a high-severity denial of service vulnerability in XenForo, published on 8 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-73321 and fix it if it is affected.\n\nWhat it is: CVE-2026-73321 is a high-severity denial of service vulnerability in XenForo, published on 8 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.\nExploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73321 exists.\n\nAffected product: XenForo. 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-2026-73321/ (Markdown: https://insights.sbomify.com/CVE-2026-73321/index.md)","id":"CVE-2026-73321","markdown":"https://insights.sbomify.com/CVE-2026-73321/index.md","name":"CVE-2026-73321","record":{"aliases":["GHSA-vv8x-44ww-j3wh"],"analysis":{"component_type":"web_application","fix_type":"upgrade","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":false,"product_category":"XenForo forum software","requires_auth":"low_privilege","summary":"Authenticated attackers can cause persistent denial of service by submitting posts with deeply nested BBCode tags, crashing PHP workers.","user_interaction":"not_required","vuln_class":"denial_of_service"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"VulnCheck","cpe":[{"product":"xenforo","vendor":"xenforo"}],"cvss":{"score":7.1,"severity":"high","source":"cna","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","version":"4.0"},"cwes":[{"id":"CWE-674","name":"Uncontrolled Recursion"}],"description":"XenForo before 2.3.13 contains an uncontrolled recursion vulnerability in the BBCode parser that allows authenticated attackers to cause persistent denial of service by submitting a post with deeply nested BBCode tags. Attackers can craft a single malicious post with sufficient nesting depth to exceed PHP's stack limit, causing fatal errors that repeatedly terminate PHP-FPM workers for all visitors rendering the affected thread.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":"2026-09-08","github_poc":1,"max_poc_stars":0,"metasploit":0,"nuclei":0,"refs":[{"date":"2026-09-08T16:36:04Z","kind":"github_poc","ref":"https://github.com/BomboBombone/CVE-2026-73321","stars":0,"title":"Sanitized XenForo write-up and proof of concept for CVE-2026-73321."}],"tier":"weaponised"},"has_fix":null,"headline":"XenForo \u003c 2.3.13 Uncontrolled Recursion DoS via BBCode Parser","id":"CVE-2026-73321","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"denial_of_service","year":"2026"},"n_packages":0,"n_references":5,"next":{"headline":"This CVE ID has been rejected or withdrawn by its CVE Numbering Authority.","id":"CVE-2026-73323"},"packages":[],"prev":{"headline":"XenForo \u003c 2.3.13 Unauthenticated Information Disclosure via Unfurl Endpoint","id":"CVE-2026-73320"},"products":["XenForo"],"published":"2026-09-08","related":[{"cvss_score":9.3,"headline":"XenForo Passkey Security Bypass","id":"CVE-2025-71279","kev_date_added":null,"published":"2026-04-01"},{"cvss_score":9.1,"headline":"XenForo \u003c 2.3.13 Authentication Bypass via OAuth2 Token Endpoint","id":"CVE-2026-73309","kev_date_added":null,"published":"2026-09-08"},{"cvss_score":9.1,"headline":"XenForo \u003c 2.3.13 OAuth2 Authorization Code Reuse","id":"CVE-2026-73311","kev_date_added":null,"published":"2026-09-08"},{"cvss_score":9.1,"headline":"XenForo \u003c 2.3.13 Refresh Token Replay via Expired Access Token","id":"CVE-2026-73312","kev_date_added":null,"published":"2026-09-08"},{"cvss_score":8.8,"headline":"Xenforo before 2.2.16 allows CSRF.","id":"CVE-2024-38457","kev_date_added":null,"published":"2024-06-16"},{"cvss_score":8.8,"headline":"Code injection in n/a","id":"CVE-2024-38458","kev_date_added":null,"published":"2024-06-16"},{"cvss_score":8.7,"headline":"XenForo \u003c 2.3.13 Signature Verification Bypass via PayPal REST Webhook","id":"CVE-2026-73314","kev_date_added":null,"published":"2026-09-08"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"},{"class":"open","licence":"CC0","name":"PoC-in-GitHub"}],"ssvc":{"automatable":"no","exploitation":"poc","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-10-01","vendors":["XenForo"]},"summary":"Authenticated attackers can cause persistent denial of service by submitting posts with deeply nested BBCode tags, crashing PHP workers.","url":"https://insights.sbomify.com/CVE-2026-73321/"}