{"id":"CVE-2026-114728","kind":"vulnerability","aliases":["CVE-2026-114728"],"related":[],"title":"Roundcube Webmail: CSS escapes bypass remote content blocking in HTML mail","description":"Roundcube Webmail before 1.6.20 and 1.7.x before 1.7.5 is affected by a remote content blocking bypass in the handling of FuncIRI attributes. rcube_washtml detected the CSS url() token with a pattern that enumerated only some of its escaped spellings, so values using other CSS escape sequences, for example \\000075rl( or u\\72 l(, were not recognized and remote content was loaded from an HTML message without the user's consent. Upstream fixed this in the commit “Fix remote content blocking bypass via CSS escapes in FuncIRI attributes (again)”, which resolves CSS escapes before matching and also inspects the `to`, `from` and `by` attributes.","summary":"Roundcube's HTML sanitizer missed CSS-escaped spellings of url(), so remote images and resources in HTML messages loaded without the user's consent. An attacker can use this to learn when a message is opened and to track the reader.","severity":"medium","cvss":5.3,"epss":0.00379,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["package","php","roundcube","self-hosted","webmail"],"not_affected_if":["patched-version","plain-text-only"],"how_to_check":"- Check the installed Roundcube version in the `program/include/iniset.php` file or the about page (`RCMAIL_VERSION`).\n- Confirm whether the remote content blocking setting is enabled for users.","fix":"- Upgrade Roundcube Webmail to `1.6.20` on the 1.6 branch or `1.7.5` on the 1.7 branch.\n- Apply the upstream commit “Fix remote content blocking bypass via CSS escapes in FuncIRI attributes (again)” if you cannot upgrade yet.","status":"open","published_at":"2026-10-22T02:17:00+00:00","first_seen_at":"2026-10-23T21:57:30+00:00","triaged_at":"2026-10-25T04:20:43+00:00","updated_at":"2026-10-25T04:20:43+00:00","category":"package","confidence":0.7,"triage":{"at":"2026-10-25T04:20:43Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade Roundcube Webmail to `1.6.20` on the 1.6 branch or `1.7.5` on the 1.7 branch.\n- Apply the upstream commit “Fix remote content blocking bypass via CSS escapes in FuncIRI attributes (again)” if you cannot upgrade yet.","reach":"internet","title":"Roundcube Webmail: CSS escapes bypass remote content blocking in HTML mail","impact":"low","summary":"Roundcube's HTML sanitizer missed CSS-escaped spellings of url(), so remote images and resources in HTML messages loaded without the user's consent. An attacker can use this to learn when a message is opened and to track the reader.","category":"package","nicknames":[],"who_cares":["roundcube","self-hosted","webmail","php"],"confidence":0.7,"needs_auth":"yes","worst_case":"remote content loads from attacker server when mail is opened","analyst_note":"","how_to_check":"- Check the installed Roundcube version in the `program/include/iniset.php` file or the about page (`RCMAIL_VERSION`).\n- Confirm whether the remote content blocking setting is enabled for users.","needs_analyst":false,"not_affected_if":["patched-version","plain-text-only"],"who_is_affected":"Any Roundcube Webmail instance on a version before 1.6.20 or before 1.7.5 that displays HTML mail is exposed. Deployments that only show plain-text mail or that run a patched release can skip it.","user_interaction":"yes","needs_special_setup":"no","severity_if_unknown":"medium"},"cost_usd":0.000629,"input_tokens":3503,"output_tokens":558,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-114728':14A,17A '-2026':13A,16A '000075rl':117C '1.6.20':70C '1.7':72C '1.7.5':75C '72':120C 'affect':77C 'also':164C 'attack':51B 'attribut':89C,155C,171C 'block':8A,82C,148C 'bypass':5A,83C,149C 'commit':144C 'consent':49B,138C 'content':7A,81C,127C,147C 'css':3A,31B,94C,112C,151C,159C 'css-escap':30B 'cve':12A,15A 'detect':92C 'enumer':101C 'escap':4A,32B,106C,113C,152C,160C 'exampl':116C 'fix':140C,145C 'funciri':88C,154C 'handl':86C 'host':23B 'html':10A,27B,42B,132C 'imag':38B 'inspect':165C 'l':121C 'learn':56B 'load':44B,129C 'mail':11A 'match':162C 'messag':43B,59B,133C 'miss':29B 'open':61B 'packag':18B 'pattern':99C 'php':19B 'rcube':90C 'reader':66B 'recogn':124C 'remot':6A,37B,80C,126C,146C 'resolv':158C 'resourc':40B 'roundcub':1A,20B,25B,67C 'sanit':28B 'self':22B 'self-host':21B 'sequenc':114C 'spell':33B,107C 'token':96C 'track':64B 'u':119C 'upstream':139C 'url':35B,95C 'use':53B,110C 'user':47B,136C 'valu':109C 'via':150C 'washtml':91C 'webmail':2A,24B,68C 'without':45B,134C 'x':73C","nicknames":[],"mitigations":[],"who_affected":"Any Roundcube Webmail instance on a version before 1.6.20 or before 1.7.5 that displays HTML mail is exposed. Deployments that only show plain-text mail or that run a patched release can skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-22T02:17:00+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","cvss_by":"cve@mitre.org","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-114728","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-114728","severity":null,"published_at":"2026-10-22T02:17:00+00:00","modified_at":"2026-10-22T16:45:49+00:00","first_seen_at":"2026-10-23T21:57:30+00:00","fetched_at":"2026-10-23T22:29:02+00:00","note":null},{"source":"epss","external_id":"CVE-2026-114728","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-114728","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-24T07:15:52+00:00","fetched_at":"2026-10-24T07:15:52+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}