{"id":"CVE-2026-114474","kind":"vulnerability","aliases":["CVE-2026-114474"],"related":[],"title":"hMailServer: forged From header lets forwarded mail pass SPF and DMARC","description":"Use of a less trusted source for the envelope sender in the external-account download of Progressive Robot hMailServer 6.0.0 through 6.3.6 allows a remote unauthenticated attacker to have mail they write in the name of a domain the server hosts sent on by the server with an envelope sender at that domain, so that it passes the domain's SPF and DMARC at other receivers. A message the server downloads from an external POP3 or IMAP account has no SMTP envelope of its own, and the server took the address in its From header as its envelope sender, whatever that address was. A forward or redirect of the downloaded message to an outside address then left with that address as its envelope sender, which the Sender Rewriting Scheme leaves alone for a hosted domain, so that the receiver's SPF check passed for the forged domain, aligned even under strict alignment, with no non-default setting, host name record or DMARC policy needed. An attacker needs to know a mailbox elsewhere that an account here collects and forwards to an outside address; an account holder who adds an external account of their own can collect from a server of their own, which matters where SmtpAuthenticatedSenderCheck holds signed-in senders to their own addresses.","summary":"hMailServer 6.0.0 through 6.3.6 takes the From header of mail downloaded from an external POP3 or IMAP account as its SMTP envelope sender. When that mail is forwarded to an outside address, the forged domain's SPF and DMARC checks pass at the receiver, so an attacker can send mail that appears to come from a hosted domain.","severity":"medium","cvss":5.9,"epss":0.00164,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["email","hmailserver","mail-forwarding","package","self-hosted"],"not_affected_if":["no-external-account-download","no-outbound-forwarding","patched-version"],"how_to_check":"- Check the installed hMailServer version; affected releases are `6.0.0` through `6.3.6`.\n- Look for accounts that collect external mail (Fetch Accounts / external account download) and forward or redirect it to outside addresses.\n- Check whether `SmtpAuthenticatedSenderCheck` is enabled.","fix":"- Upgrade hMailServer to a release later than `6.3.6`; unknown which exact version contains the fix.\n- Disable external account download and forwarding to outside addresses until patched, if feasible.","status":"open","published_at":"2026-10-21T16:17:34+00:00","first_seen_at":"2026-10-23T21:57:29+00:00","triaged_at":"2026-10-25T04:08:05+00:00","updated_at":"2026-10-25T04:08:05+00:00","category":"package","confidence":0.7,"triage":{"at":"2026-10-25T04:08:05Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade hMailServer to a release later than `6.3.6`; unknown which exact version contains the fix.\n- Disable external account download and forwarding to outside addresses until patched, if feasible.","reach":"internet","title":"hMailServer: forged From header lets forwarded mail pass SPF and DMARC","impact":"medium","summary":"hMailServer 6.0.0 through 6.3.6 takes the From header of mail downloaded from an external POP3 or IMAP account as its SMTP envelope sender. When that mail is forwarded to an outside address, the forged domain's SPF and DMARC checks pass at the receiver, so an attacker can send mail that appears to come from a hosted domain.","category":"package","nicknames":[],"who_cares":["hmailserver","self-hosted","email","mail-forwarding"],"confidence":0.7,"needs_auth":"no","worst_case":"Attacker sends mail spoofing a hosted domain that passes SPF and DMARC","analyst_note":"Confirm the fixed version and the exact feature name for external account download and forwarding from the NVD entry or vendor advisory.","how_to_check":"- Check the installed hMailServer version; affected releases are `6.0.0` through `6.3.6`.\n- Look for accounts that collect external mail (Fetch Accounts / external account download) and forward or redirect it to outside addresses.\n- Check whether `SmtpAuthenticatedSenderCheck` is enabled.","needs_analyst":true,"not_affected_if":["no-external-account-download","no-outbound-forwarding","patched-version"],"who_is_affected":"Servers running hMailServer 6.0.0 through 6.3.6 that download mail from external POP3 or IMAP accounts and forward or redirect it to addresses outside the server. An attacker needs to know a mailbox the server collects from and forwards onward; an account holder can also add an external account pointing at a server they control. Servers without external account download or outbound forwarding are less exposed.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"medium"},"cost_usd":0.000722,"input_tokens":3636,"output_tokens":717,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-114474':14A,17A '-2026':13A,16A '6.0.0':28B,105C '6.3.6':30B,107C 'account':44B,99C,163C,261C,271C,277C 'add':274C 'address':58B,176C,187C,200C,205C,269C,301C 'align':233C,237C 'allow':108C 'alon':216C 'appear':78B 'attack':73B,112C,252C 'check':66B,227C 'collect':263C,282C 'come':80B 'cve':12A,15A 'default':242C 'dmarc':11A,65B,148C,248C 'domain':61B,84B,123C,138C,144C,220C,232C 'download':37B,100C,156C,195C 'elsewher':258C 'email':18B 'envelop':48B,93C,134C,167C,183C,208C 'even':234C 'extern':40B,98C,159C,276C 'external-account':97C 'forg':2A,60B,231C 'forward':6A,22B,54B,190C,265C 'header':4A,34B,180C 'hmailserv':1A,19B,27B,104C 'hold':293C 'holder':272C 'host':26B,83B,126C,219C,244C 'imap':43B,162C 'know':255C 'leav':215C 'left':202C 'less':88C 'let':5A 'mail':7A,21B,36B,52B,76B,115C 'mail-forward':20B 'mailbox':257C 'matter':290C 'messag':153C,196C 'name':120C,245C 'need':250C,253C 'non':241C 'non-default':240C 'outsid':57B,199C,268C 'packag':23B 'pass':8A,67B,142C,228C 'polici':249C 'pop3':41B,160C 'progress':102C 'receiv':70B,151C,224C 'record':246C 'redirect':192C 'remot':110C 'rewrit':213C 'robot':103C 'scheme':214C 'self':25B 'self-host':24B 'send':75B 'sender':49B,94C,135C,184C,209C,212C,297C 'sent':127C 'server':125C,131C,155C,173C,285C 'set':243C 'sign':295C 'signed-in':294C 'smtp':47B,166C 'smtpauthenticatedsendercheck':292C 'sourc':90C 'spf':9A,63B,146C,226C 'strict':236C 'take':31B 'took':174C 'trust':89C 'unauthent':111C 'use':85C 'whatev':185C 'write':117C","nicknames":[],"mitigations":[],"who_affected":"Servers running hMailServer 6.0.0 through 6.3.6 that download mail from external POP3 or IMAP accounts and forward or redirect it to addresses outside the server. An attacker needs to know a mailbox the server collects from and forwards onward; an account holder can also add an external account pointing at a server they control. Servers without external account download or outbound forwarding are less exposed.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-21T16:17:34+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N","cvss_by":"cve@gitlab.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-114474","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-114474","severity":null,"published_at":"2026-10-21T16:17:34+00:00","modified_at":"2026-10-22T16:18:19+00:00","first_seen_at":"2026-10-23T21:57:29+00:00","fetched_at":"2026-10-23T22:29:01+00:00","note":null},{"source":"epss","external_id":"CVE-2026-114474","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-114474","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-24T13:15:54+00:00","fetched_at":"2026-10-24T13:15:54+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"}