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.
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{
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"cveMetadata": {
"cveId": "CVE-2026-116271",
"assignerOrgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
"assignerShortName": "CPANSec",
"dateUpdated": "2026-10-28T17:34:06.757Z",
"dateReserved": "2026-10-25T18:05:02.236Z",
"datePublished": "2026-10-28T17:34:06.757Z",
"state": "PUBLISHED"
},
"containers": {
"cna": {
"providerMetadata": {
"orgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
"shortName": "CPANSec",
"dateUpdated": "2026-10-28T17:34:06.757Z"
},
"title": "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",
"descriptions": [
{
"lang": "en",
"value": "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.\n\nEach 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.\n\nWhen 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."
}
],
"affected": [
{
"collectionURL": "https://cpan.org/modules",
"packageName": "MIME-tools",
"modules": [
"MIME::Parser::FileUnder"
],
"programFiles": [
"lib/MIME/Parser/Filer.pm",
"lib/MIME/Body.pm"
],
"programRoutines": [
{
"name": "MIME::Parser::FileUnder::init_parse"
},
{
"name": "MIME::Parser::Filer::find_unused_path"
}
],
"repo": "https://salsa.debian.org/dskoll/mime-tools",
"defaultStatus": "unaffected",
"versions": [
{
"version": "0",
"status": "affected",
"versionType": "custom",
"lessThan": "5.521"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"lang": "en",
"description": "CWE-59 Improper Link Resolution Before File Access ('Link Following')",
"cweId": "CWE-59",
"type": "CWE"
}
]
}
],
"references": [
{
"url": "https://metacpan.org/release/DSKOLL/MIME-tools-5.521/changes",
"tags": [
"release-notes"
]
}
],
"solutions": [
{
"lang": "en",
"value": "Upgrade to MIME-tools 5.521 or later."
}
]
}
}
}