/ 
MIME-tools-5.520
/ MIME::Field::ParamVal
Security Advisories (10)
CVE-2026-116264 (2026-10-28)

MIME::Field::ParamVal versions before 5.521 for Perl allow one invalid Content-Type parameter to hide the parameters after it, including the multipart boundary. Parameter parsing stops at the first parameter whose name it cannot read, such as x:y=1 or a name containing an 8-bit byte, and drops every parameter after it. When the boundary is among them, MIME::Parser keeps the multipart body as a single undecoded part without marking the parse as ambiguous. Mail readers that skip the invalid parameter still find the boundary. A remote sender can hide an attachment from a filter that relies on ambiguous_content() while the recipient's mail client shows it.

CVE-2026-116265 (2026-10-28)

MIME::Field::ParamVal versions before 5.521 for Perl do not flag an ambiguous multipart boundary written as RFC 2231 continuations. The boundary ambiguity checks look only at a plain boundary= parameter, and a boundary split into RFC 2231 sections (boundary*0=, boundary*1= and so on) is joined after they have run. A repeated section number is concatenated rather than reported as a duplicate. From version 5.518, an encoded word or trailing whitespace in such a boundary also goes unflagged, although multipart_boundary() decodes or strips it. A remote sender can make MIME::Parser split a message on a different boundary than other mail readers, hiding an attachment from a filter that relies on ambiguous_content() while the recipient's mail client shows it.

CVE-2026-116266 (2026-10-28)

MIME::Head versions from 5.518 before 5.521 for Perl decode a partly encoded multipart boundary without flagging the parse as ambiguous. The multipart_boundary() method decodes RFC 2047 encoded words anywhere in the boundary, but the ambiguity check only fires when the whole value is one encoded word. A boundary such as abc=?us-ascii?Q?def?= is used as abcdef, and ambiguous_content() returns false. Encoded words are not allowed in parameters, so other mail readers split the message on the literal value. A remote sender can hide an attachment from a filter that relies on ambiguous_content() while the recipient's mail client shows it.

CVE-2026-116267 (2026-10-28)

MIME::Parser versions before 5.521 for Perl allow memory exhaustion via indented error messages from a truncated, deeply nested message. Each stored parser diagnostic is indented by three spaces per nesting level. When a message nested N levels deep ends without its closing boundaries, every level logs an error at its own depth, so the stored diagnostics grow with the square of N. The defaults place no limit on nesting depth.

CVE-2026-116268 (2026-10-28)

MIME::Field::ParamVal versions before 5.521 for Perl allow CPU exhaustion via unclosed comments in header parameters. The comment pattern used to parse Content-Type and Content-Disposition parameters scans from each "(" to the next ")". In a field with no ")", every "(" scans to the end of the header and fails, so parsing takes time quadratic in the header length. The field is parsed again on each attribute lookup, several times per MIME entity. A 40 KB header takes about 7 seconds to parse once.

CVE-2026-116269 (2026-10-28)

MIME::Field::ParamVal versions before 5.521 for Perl turn an RFC 2231 filename with a hyphenated language tag into an empty recommended filename. A 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. Other mail readers return payload.exe. A remote sender can get an attachment past a policy that checks file extensions on the recommended filename.

CVE-2026-116270 (2026-10-28)

MIME::Words versions before 5.521 for Perl allow memory exhaustion via repeated "=?" sequences in decode_mimewords. For each "=?" that does not start a complete encoded word, decode_mimewords appends an error message containing the whole input string to $@. A boundary of 8,000 "=?" pairs (16,000 bytes) adds 8,000 copies of itself to $@, about 128 MB. From version 5.518, MIME::Parser decodes every multipart boundary this way, so a remote sender can exhaust the memory of the parsing process with one Content-Type header.

CVE-2026-116271 (2026-10-28)

MIME::Parser::FileUnder versions before 5.521 for Perl reuse a pre-created output directory and follow symlinks in it, letting local users redirect attachment writes. Each message is written to a directory named msg-<time>-<pid>-<n> under the output base, and an existing directory of that name is used as is. A file name counts as unused when nothing exists at that path, which holds for a dangling symlink, and the body file is then opened in a way that follows the link. When the output base is writable by other users, as with output_under("/tmp"), a local user can pre-create the directory with a symlink named like an attachment. The parser then writes the attachment to the link target with the privileges of the parsing process.

CVE-2026-116272 (2026-10-28)

MIME::Field::ParamVal versions before 5.521 for Perl do not flag a duplicate boundary parameter whose name contains a nested comment. A parameter written boundary((c))="A" or boundary(\))="A" is stored under that literal name rather than as boundary. A second boundary parameter is then not reported as a duplicate, and MIME::Parser splits the message on it. Readers that skip comments as RFC 5322 allows take the first boundary instead. A remote sender can hide an attachment from a filter that relies on ambiguous_content() while the recipient's mail client shows it.

CVE-2026-116273 (2026-10-28)

MIME::Parser versions before 5.521 for Perl set no limit on the number of message parts by default, allowing memory exhaustion. The max_parts option defaulted to -1, which disables the limit, so a parser created with default settings builds an entity for every part however many a message has. Version 5.521 sets max_parts to 1000 and max_depth to 64 by default. Setting either to -1 still removes the limit.

NAME

MIME::Field::ParamVal - subclass of Mail::Field, for structured MIME fields

SYNOPSIS

    # Create an object for a content-type field:
    $field = new Mail::Field 'Content-type';

    # Set some attributes:
    $field->param('_'        => 'text/html');
    $field->param('charset'  => 'us-ascii');
    $field->param('boundary' => '---ABC---');

    # Same:
    $field->set('_'        => 'text/html',
		'charset'  => 'us-ascii',
		'boundary' => '---ABC---');

    # Get an attribute, or undefined if not present:
    print "no id!"  if defined($field->param('id'));

    # Same, but use empty string for missing values:
    print "no id!"  if ($field->paramstr('id') eq '');

    # Output as string:
    print $field->stringify, "\n";

DESCRIPTION

This is an abstract superclass of most MIME fields. It handles fields with a general syntax like this:

    Content-Type: Message/Partial;
	number=2; total=3;
	id="oc=jpbe0M2Yt4s@thumper.bellcore.com"

Comments are supported between items, like this:

    Content-Type: Message/Partial; (a comment)
	number=2  (another comment) ; (yet another comment) total=3;
	id="oc=jpbe0M2Yt4s@thumper.bellcore.com"

PUBLIC INTERFACE

set [\%PARAMHASH | KEY=>VAL,...,KEY=>VAL]

Instance method. Set this field. The paramhash should contain parameter names in all lowercase, with the special "_" parameter name signifying the "default" (unnamed) parameter for the field:

   # Set up to be...
   #
   #     Content-type: Message/Partial; number=2; total=3; id="ocj=pbe0M2"
   #
   $conttype->set('_'       => 'Message/Partial',
		  'number'  => 2,
		  'total'   => 3,
		  'id'      => "ocj=pbe0M2");

Note that a single argument is taken to be a reference to a paramhash, while multiple args are taken to be the elements of the paramhash themselves.

Supplying undef for a hashref, or an empty set of values, effectively clears the object.

The self object is returned.

parse_params STRING

Class/instance utility method. Extract parameter info from a structured field, and return it as a hash reference. For example, here is a field with parameters:

    Content-Type: Message/Partial;
	number=2; total=3;
	id="oc=jpbe0M2Yt4s@thumper.bellcore.com"

Here is how you'd extract them:

    $params = $class->parse_params('content-type');
    if ($$params{'_'} eq 'message/partial') {
	$number = $$params{'number'};
	$total  = $$params{'total'};
	$id     = $$params{'id'};
    }

Like field names, parameter names are coerced to lowercase. The special '_' parameter means the default parameter for the field.

NOTE: This has been provided as a public method to support backwards compatibility, but you probably shouldn't use it.

parse STRING

Class/instance method. Parse the string into the instance. Any previous information is wiped. The self object is returned.

May also be used as a constructor.

param PARAMNAME,[VALUE]

Instance method. Return the given parameter, or undef if it isn't there. With argument, set the parameter to that VALUE. The PARAMNAME is case-insensitive. A "_" refers to the "default" parameter.

paramstr PARAMNAME,[VALUE]

Instance method. Like param(): return the given parameter, or empty if it isn't there. With argument, set the parameter to that VALUE. The PARAMNAME is case-insensitive. A "_" refers to the "default" parameter.

stringify

Instance method. Convert the field to a string, and return it.

tag

Instance method, abstract. Return the tag for this field.

SEE ALSO

Mail::Field