{"id":"CVE-2026-116269","kind":"vulnerability","aliases":["CVE-2026-116269"],"related":[],"title":"Perl MIME::Field::ParamVal: hyphenated RFC 2231 language tag hides attachment filename","description":"MIME::Field::ParamVal versions before 5.521 for Perl turn an RFC 2231 filename with a hyphenated language tag into an empty recommended filename.\n\nA parameter such as filename*=utf-8'en-US'payload.exe is converted to an encoded word with the language tag appended to the charset. The decoder strips the language suffix only when it is a single word, so it cannot resolve the charset UTF-8*EN-US and returns an empty string. The recommended_filename() method returns that empty string rather than falling back to the name parameter.\n\nOther mail readers return payload.exe. A remote sender can get an attachment past a policy that checks file extensions on the recommended filename.","summary":"MIME::Field::ParamVal before 5.521 for Perl decodes an RFC 2231 filename with a hyphenated language tag, such as en-US, to an empty string instead of the real filename. A mail filter that checks extensions on the recommended filename can then pass an executable attachment such as payload.exe.","severity":"low","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["email-security","mail-gateway","package","perl"],"not_affected_if":["filename-not-used-for-policy","no-mime-parsing"],"how_to_check":"- Run `perl -MMIME::Field::ParamVal -e 'print $MIME::Field::ParamVal::VERSION'` or `cpanm --info MIME::Field::ParamVal` to read the installed version\n- Search dependencies for `MIME::Field::ParamVal` or `MIME::Tools` to find code that calls `recommended_filename()`","fix":"- Upgrade MIME::Field::ParamVal to `5.521` or later\n- Where a filter depends on the attachment name, fall back to the `name` parameter when `recommended_filename()` returns an empty string","status":"open","published_at":"2026-10-28T18:17:13+00:00","first_seen_at":"2026-10-28T18:34:33+00:00","triaged_at":"2026-10-28T18:35:27+00:00","updated_at":"2026-10-28T18:35:27+00:00","category":"package","confidence":0.6,"triage":{"at":"2026-10-28T18:35:27Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade MIME::Field::ParamVal to `5.521` or later\n- Where a filter depends on the attachment name, fall back to the `name` parameter when `recommended_filename()` returns an empty string","reach":"network","title":"Perl MIME::Field::ParamVal: hyphenated RFC 2231 language tag hides attachment filename","impact":"medium","summary":"MIME::Field::ParamVal before 5.521 for Perl decodes an RFC 2231 filename with a hyphenated language tag, such as en-US, to an empty string instead of the real filename. A mail filter that checks extensions on the recommended filename can then pass an executable attachment such as payload.exe.","category":"package","nicknames":[],"who_cares":["perl","mail-gateway","email-security"],"confidence":0.6,"needs_auth":"no","worst_case":"Executable attachment passes an extension-based filename policy unnoticed","analyst_note":"","how_to_check":"- Run `perl -MMIME::Field::ParamVal -e 'print $MIME::Field::ParamVal::VERSION'` or `cpanm --info MIME::Field::ParamVal` to read the installed version\n- Search dependencies for `MIME::Field::ParamVal` or `MIME::Tools` to find code that calls `recommended_filename()`","needs_analyst":false,"not_affected_if":["no-mime-parsing","filename-not-used-for-policy"],"who_is_affected":"Teams whose Perl code parses inbound MIME mail and uses recommended_filename() to decide whether an attachment is allowed, for example a mail gateway or scanner built on Perl. Code that does not read attachment names from mail, or that already uses a different filename source, is not exposed by this flaw.","user_interaction":"no","needs_special_setup":"no","severity_if_unknown":"low"},"cost_usd":0.000663,"input_tokens":3442,"output_tokens":638,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-116269':15A,18A '-2026':14A,17A '-8':106C,145C '2231':7A,37B,88C '5.521':31B,82C 'append':121C 'attach':11A,73B,181C 'back':165C 'cannot':140C 'charset':124C,143C 'check':62B,186C 'convert':112C 'cve':13A,16A 'decod':34B,126C 'email':20B 'email-secur':19B 'empti':51B,97C,152C,160C 'en':47B,108C,147C 'en-us':46B,107C,146C 'encod':115C 'execut':72B 'extens':63B,188C 'fall':164C 'field':3A,28B,78C 'file':187C 'filenam':12A,38B,57B,67B,89C,99C,104C,156C,192C 'filter':60B 'gateway':24B 'get':179C 'hide':10A 'hyphen':5A,41B,92C 'instead':53B 'languag':8A,42B,93C,119C,129C 'mail':23B,59B,171C 'mail-gateway':22B 'method':157C 'mime':2A,27B,77C 'name':168C 'packag':25B 'paramet':101C,169C 'paramv':4A,29B,79C 'pass':70B 'past':182C 'payload.exe':76B,110C,174C 'perl':1A,26B,33B,84C 'polici':184C 'rather':162C 'reader':172C 'real':56B 'recommend':66B,98C,155C,191C 'remot':176C 'resolv':141C 'return':150C,158C,173C 'rfc':6A,36B,87C 'secur':21B 'sender':177C 'singl':136C 'string':52B,153C,161C 'strip':127C 'suffix':130C 'tag':9A,43B,94C,120C 'turn':85C 'us':48B,109C,148C 'utf':105C,144C 'version':80C 'word':116C,137C","nicknames":[],"mitigations":[],"who_affected":"Teams whose Perl code parses inbound MIME mail and uses recommended_filename() to decide whether an attachment is allowed, for example a mail gateway or scanner built on Perl. Code that does not read attachment names from mail, or that already uses a different filename source, is not exposed by this flaw.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-28T18:17:13+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-116269","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-116269","severity":null,"published_at":"2026-10-28T18:17:13+00:00","modified_at":"2026-10-28T18:17:13+00:00","first_seen_at":"2026-10-28T18:34:33+00:00","fetched_at":"2026-10-28T18:34:33+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"}