MIME::Words up to 5.520 MIME Word Decoder decode_mimewords memory allocation

Summaryinfo

A vulnerability was found in MIME::Words up to 5.520. It has been declared as problematic. The affected element is the function decode_mimewords of the component MIME Word Decoder. Such manipulation leads to memory allocation. This vulnerability is documented as CVE-2026-116270. The attack can be executed remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in MIME::Words up to 5.520 and classified as problematic. Affected by this issue is the function decode_mimewords of the component MIME Word Decoder. The manipulation with an unknown input leads to a memory allocation vulnerability. Using CWE to declare the problem leads to CWE-789. The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated. Impacted is availability. CVE summarizes:

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.

The advisory is available at metacpan.org. This vulnerability is handled as CVE-2026-116270 since 10/25/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are known, but there is no available exploit.

Upgrading to version 5.521 eliminates this vulnerability.

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Productinfo

Name

• MIME::Words

Version

• 5.520

CPE 2.3info

• 🔒

CPE 2.2info

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