{"id":"GHSA-x6mj-8jx9-qhqv","kind":"vulnerability","aliases":["GHSA-x6mj-8jx9-qhqv"],"related":[],"title":"Possible sensitive session information leak in Active Storage proxy mode","description":"### Impact\nWhen `ActionDispatch::Cookies` reads a signed or encrypted cookie that was written under a rotated secret (`config.action_dispatch.cookies_rotations`) or in the format that a `:hybrid` cookie serializer migrates from, it writes the cookie back to the response in the current format, and that write ignores `request.session_options[:skip]`. `ActiveStorage::DisableSession` relies on that option to keep the session cookie off the public, immutable responses of the Active Storage proxy controllers, but those controllers still load the session, so a request carrying an old-format session cookie could receive the rewritten session cookie in `Set-Cookie` on a cacheable response. A shared cache that stores such a response together with its `Set-Cookie` header could then serve one user's session to later requesters of the same URL, or serve an attacker's session to other users.\n\nApplications are affected when they serve Active Storage files through the proxy controllers, have a cookie rotation or a `:hybrid` serializer migration configured, and run behind a cache that stores `Set-Cookie` on public responses. This is a path around the fix for [CVE-2024-26144](https://github.com/advisories/GHSA-8h22-8cf7-hq6g).\n\n### Details\nIn the fixed releases, a response that skips the session leaves an old-format signed or encrypted cookie unchanged, and the next request that does not skip the session upgrades it. An application that skips the session on every request no longer upgrades its signed or encrypted cookies. Cookies that the application sets explicitly are still written. See the Action Pack CHANGELOG.\n\n### Workarounds\nConfigure caching proxies not to store responses that carry a `Set-Cookie` header, or complete the cookie rotation or serializer migration and remove it from the configuration.\n\n### Releases\nThe fixed releases are available at the normal locations.\n\nPatches for those who cannot upgrade at once:\n- 8.1: https://github.com/rails/rails/commit/849a6c30eacbb6ca4722132f43c4333a93188556.patch\n- 8.0: https://github.com/rails/rails/commit/0e6cf8faa89caf4c64311d35ca2bc88c1458d4e3.patch\n\n### Credit\nThis issue was responsibly reported by HackerOne researcher [flashmyname](https://hackerone.com/flashmyname).","summary":"Action Pack writes a rotated or hybrid-migrated session cookie back into responses that were meant to skip the session, which Active Storage proxy controllers use for public files. A shared cache storing those responses could hand one user's session to others.","severity":"medium","cvss":6.8,"epss":null,"exploited":false,"exploited_at":null,"products":[{"name":"actionpack","fixed":["8.1.4.1"],"affected":">= 8.1, < 8.1.4.1","ecosystem":"rubygems"},{"name":"actionpack","fixed":["8.0.5.2"],"affected":"< 8.0.5.2","ecosystem":"rubygems"}],"ecosystems":["rubygems"],"tags":["actionpack","active-storage","cwe-200","package","rails","self-hosted"],"not_affected_if":["direct-storage-urls","no-caching-proxy","no-cookie-rotation"],"how_to_check":"- Check the Action Pack version with `bundle exec rails -e production 'puts Gem::Specs.find_by_name(\"actionpack\").version'` or `bundle list | grep actionpack`, looking for versions below `8.1.4.1` or below `8.0.5.2`.\n- Search `config/` for `cookies_rotations` or a `:hybrid` cookie serializer migration.\n- Confirm whether Active Storage files are served through the proxy controllers and whether a cache stores `Set-Cookie` on those responses.","fix":"- Upgrade actionpack 8.1 branch to `8.1.4.1`.\n- Upgrade actionpack 8.0 branch to `8.0.5.2`.\n- Patches for teams that cannot upgrade yet are linked in the advisory (commits 849a6c30 for 8.1 and 0e6cf8fa for 8.0).","status":"open","published_at":"2026-11-04T03:02:15+00:00","first_seen_at":"2026-11-09T22:53:28+00:00","triaged_at":"2026-11-09T22:54:37+00:00","updated_at":"2026-11-09T22:54:37+00:00","category":"package","confidence":0.8,"triage":{"at":"2026-11-09T22:54:37Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade actionpack 8.1 branch to `8.1.4.1`.\n- Upgrade actionpack 8.0 branch to `8.0.5.2`.\n- Patches for teams that cannot upgrade yet are linked in the advisory (commits 849a6c30 for 8.1 and 0e6cf8fa for 8.0).","reach":"internet","title":"Rails Action Pack: session cookie can leak into cacheable Active Storage responses","impact":"medium","summary":"Action Pack writes a rotated or hybrid-migrated session cookie back into responses that were meant to skip the session, which Active Storage proxy controllers use for public files. A shared cache storing those responses could hand one user's session to others.","audience":"businesses","category":"package","nicknames":[],"who_cares":["rails","actionpack","active-storage","self-hosted"],"confidence":0.8,"fix_status":"available","needs_auth":"unknown","worst_case":"a shared cache serves one user's session cookie to others","analyst_note":"","how_to_check":"- Check the Action Pack version with `bundle exec rails -e production 'puts Gem::Specs.find_by_name(\"actionpack\").version'` or `bundle list | grep actionpack`, looking for versions below `8.1.4.1` or below `8.0.5.2`.\n- Search `config/` for `cookies_rotations` or a `:hybrid` cookie serializer migration.\n- Confirm whether Active Storage files are served through the proxy controllers and whether a cache stores `Set-Cookie` on those responses.","plain_action":"","product_name":"","needs_analyst":false,"not_affected_if":["direct-storage-urls","no-cookie-rotation","no-caching-proxy"],"who_is_affected":"Applications that serve Active Storage files through the proxy controllers, use a cookie rotation or a :hybrid serializer migration, and sit behind a cache that stores Set-Cookie on public responses. Apps that do not proxy Active Storage files, or that do not run such a cache, are unlikely to be exposed.","user_interaction":"no","product_ecosystem":"","needs_special_setup":"yes","severity_if_unknown":"unknown"},"cost_usd":0.000907,"input_tokens":5341,"output_tokens":746,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-200':28B '-2024':263C '-26144':264C '/advisories/ghsa-8h22-8cf7-hq6g).':267C '/flashmyname).':399C '/rails/rails/commit/0e6cf8faa89caf4c64311d35ca2bc88c1458d4e3.patch':386C '/rails/rails/commit/849a6c30eacbb6ca4722132f43c4333a93188556.patch':382C '8.0':383C '8.1':379C '8jx9':14A,19A 'action':34B,329C 'actiondispatch':80C 'actionpack':21A,22A,23B 'activ':7A,25B,56B,145C,224C 'active-storag':24B 'activestorag':127C 'affect':220C 'applic':218C,302C,321C 'around':258C 'attack':212C 'avail':366C 'back':45B,112C 'behind':243C 'cach':66B,182C,245C,334C 'cacheabl':178C 'cannot':375C 'carri':159C,341C 'changelog':331C 'complet':348C 'config.action_dispatch.cookies':95C 'configur':240C,333C,360C 'control':59B,148C,151C,230C 'cooki':44B,81C,87C,104C,111C,137C,165C,171C,175C,193C,233C,250C,287C,317C,318C,345C,350C 'could':70B,166C,195C 'credit':387C 'current':118C 'cve':262C 'cwe':27B 'detail':268C 'disablesess':128C 'encrypt':86C,286C,316C 'everi':308C 'explicit':323C 'file':63B,226C 'fix':260C,271C,363C 'flashmynam':396C 'format':100C,119C,163C,283C 'ghsa':12A,17A 'ghsa-x6mj-8jx9-qhqv':11A,16A 'github.com':266C,381C,385C 'github.com/advisories/ghsa-8h22-8cf7-hq6g).':265C 'github.com/rails/rails/commit/0e6cf8faa89caf4c64311d35ca2bc88c1458d4e3.patch':384C 'github.com/rails/rails/commit/849a6c30eacbb6ca4722132f43c4333a93188556.patch':380C 'hackeron':394C 'hackerone.com':398C 'hackerone.com/flashmyname).':397C 'hand':71B 'header':194C,346C 'host':33B 'hybrid':41B,103C,237C 'hybrid-migr':40B 'ignor':123C 'immut':141C 'impact':78C 'inform':4A 'issu':389C 'keep':134C 'later':203C 'leak':5A 'leav':279C 'load':153C 'locat':370C 'longer':311C 'meant':50B 'migrat':42B,106C,239C,354C 'mode':10A 'next':291C 'normal':369C 'old':162C,282C 'old-format':161C,281C 'one':72B,198C 'option':125C,132C 'other':77B 'pack':35B,330C 'packag':29B 'patch':371C 'path':257C 'possibl':1A 'proxi':9A,58B,147C,229C,335C 'public':62B,140C,252C 'qhqv':15A,20A 'rail':30B 'read':82C 'receiv':167C 'releas':272C,361C,364C 'reli':129C 'remov':356C 'report':392C 'request':158C,204C,292C,309C 'request.session':124C 'research':395C 'respons':47B,69B,115C,142C,179C,187C,253C,274C,339C,391C 'rewritten':169C 'rotat':38B,93C,96C,234C,351C 'run':242C 'secret':94C 'see':327C 'self':32B 'self-host':31B 'sensit':2A 'serial':105C,238C,353C 'serv':197C,210C,223C 'session':3A,43B,54B,75B,136C,155C,164C,170C,201C,214C,278C,298C,306C 'set':174C,192C,249C,322C,344C 'set-cooki':173C,191C,248C,343C 'share':65B,181C 'sign':84C,284C,314C 'skip':52B,126C,276C,296C,304C 'still':152C,325C 'storag':8A,26B,57B,146C,225C 'store':67B,184C,247C,338C 'togeth':188C 'unchang':288C 'upgrad':299C,312C,376C 'url':208C 'use':60B 'user':73B,199C,217C 'workaround':332C 'write':36B,109C,122C 'written':90C,326C 'x6mj':13A,18A","nicknames":[],"mitigations":[],"who_affected":"Applications that serve Active Storage files through the proxy controllers, use a cookie rotation or a :hybrid serializer migration, and sit behind a cache that stores Set-Cookie on public responses. Apps that do not proxy Active Storage files, or that do not run such a cache, are unlikely to be exposed.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"pkeys":["actionpack"],"ptokens":["actionpack"],"labels":["actionpack","activestorage","cwe200","medium","package","rails","rubygems","selfhosted"],"campaign_type":null,"search_a":"'8jx9':14A,19A 'actionpack':21A,22A 'activ':7A 'ghsa':12A,17A 'ghsa-x6mj-8jx9-qhqv':11A,16A 'inform':4A 'leak':5A 'mode':10A 'possibl':1A 'proxi':9A 'qhqv':15A,20A 'sensit':2A 'session':3A 'storag':8A 'x6mj':13A,18A","search_b":"'-200':28B 'action':34B 'actionpack':23B 'activ':25B,56B 'active-storag':24B 'back':45B 'cach':66B 'control':59B 'cooki':44B 'could':70B 'cwe':27B 'file':63B 'hand':71B 'host':33B 'hybrid':41B 'hybrid-migr':40B 'meant':50B 'migrat':42B 'one':72B 'other':77B 'pack':35B 'packag':29B 'proxi':58B 'public':62B 'rail':30B 'respons':47B,69B 'rotat':38B 'self':32B 'self-host':31B 'session':43B,54B,75B 'share':65B 'skip':52B 'storag':26B,57B 'store':67B 'use':60B 'user':73B 'write':36B","search_c":"'-2024':263C '-26144':264C '/advisories/ghsa-8h22-8cf7-hq6g).':267C '/flashmyname).':399C '/rails/rails/commit/0e6cf8faa89caf4c64311d35ca2bc88c1458d4e3.patch':386C '/rails/rails/commit/849a6c30eacbb6ca4722132f43c4333a93188556.patch':382C '8.0':383C '8.1':379C 'action':329C 'actiondispatch':80C 'activ':145C,224C 'activestorag':127C 'affect':220C 'applic':218C,302C,321C 'around':258C 'attack':212C 'avail':366C 'back':112C 'behind':243C 'cach':182C,245C,334C 'cacheabl':178C 'cannot':375C 'carri':159C,341C 'changelog':331C 'complet':348C 'config.action_dispatch.cookies':95C 'configur':240C,333C,360C 'control':148C,151C,230C 'cooki':81C,87C,104C,111C,137C,165C,171C,175C,193C,233C,250C,287C,317C,318C,345C,350C 'could':166C,195C 'credit':387C 'current':118C 'cve':262C 'detail':268C 'disablesess':128C 'encrypt':86C,286C,316C 'everi':308C 'explicit':323C 'file':226C 'fix':260C,271C,363C 'flashmynam':396C 'format':100C,119C,163C,283C 'github.com':266C,381C,385C 'github.com/advisories/ghsa-8h22-8cf7-hq6g).':265C 'github.com/rails/rails/commit/0e6cf8faa89caf4c64311d35ca2bc88c1458d4e3.patch':384C 'github.com/rails/rails/commit/849a6c30eacbb6ca4722132f43c4333a93188556.patch':380C 'hackeron':394C 'hackerone.com':398C 'hackerone.com/flashmyname).':397C 'header':194C,346C 'hybrid':103C,237C 'ignor':123C 'immut':141C 'impact':78C 'issu':389C 'keep':134C 'later':203C 'leav':279C 'load':153C 'locat':370C 'longer':311C 'migrat':106C,239C,354C 'next':291C 'normal':369C 'old':162C,282C 'old-format':161C,281C 'one':198C 'option':125C,132C 'pack':330C 'patch':371C 'path':257C 'proxi':147C,229C,335C 'public':140C,252C 'read':82C 'receiv':167C 'releas':272C,361C,364C 'reli':129C 'remov':356C 'report':392C 'request':158C,204C,292C,309C 'request.session':124C 'research':395C 'respons':115C,142C,179C,187C,253C,274C,339C,391C 'rewritten':169C 'rotat':93C,96C,234C,351C 'run':242C 'secret':94C 'see':327C 'serial':105C,238C,353C 'serv':197C,210C,223C 'session':136C,155C,164C,170C,201C,214C,278C,298C,306C 'set':174C,192C,249C,322C,344C 'set-cooki':173C,191C,248C,343C 'share':181C 'sign':84C,284C,314C 'skip':126C,276C,296C,304C 'still':152C,325C 'storag':146C,225C 'store':184C,247C,338C 'togeth':188C 'unchang':288C 'upgrad':299C,312C,376C 'url':208C 'user':199C,217C 'workaround':332C 'write':109C,122C 'written':90C,326C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-04T03:02:15+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"ghsa-repo","external_id":"GHSA-x6mj-8jx9-qhqv","url":"https://github.com/rails/rails/security/advisories/GHSA-x6mj-8jx9-qhqv","severity":"medium","published_at":"2026-11-04T03:02:15+00:00","modified_at":"2026-11-04T03:02:15+00:00","first_seen_at":"2026-11-09T22:53:28+00:00","fetched_at":"2026-11-09T22:53:28+00:00","note":null}],"documents":[{"id":110665,"url":"https://github.com/rails/rails/security/advisories/GHSA-x6mj-8jx9-qhqv","title":"Maintainer's advisory: github.com","kind":"vendor","source":"ghsa-repo","publisher":"vendor","text":null,"published_at":null,"relation":"advisory","confidence":null,"note":"Maintainer's advisory: github.com"}],"disclosures":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}