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CVE-2026-116265— MIME::Field::ParamVal versions before 5.521 for Perl do not flag an ambiguous multipart boundary written as RFC 2231 continuations

Quick assessment

Affected
CVE-2026-116265
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Perl 的 MIME::Field::ParamVal 模块在 5.521 版本之前，无法正确标识以 RFC 2231 续行形式编写的歧义多部分边界（multipart boundary）。 该模块的边界歧义检查仅针对普通的 参数进行；而对于被拆分为 RFC 2231 分段（如 、 等）的边界，系统会在检查完成后再将其拼接。因此，若出现重复的分段编号，系统会将其直接拼接，而不会将其报告为重复项。自 5.518 版本起，若此类边界中包含编码字（encoded word）或尾部空白字符，同样不会被标记为歧义，尽管 方

AI Predicted 6.5 Difficulty: Moderate EPSS 0.18% · P7

Affected Version Matrix 1

VendorProduct Version RangeStatus
None None < 5.521 affected

I. Basic Information for CVE-2026-116265

Vulnerability Information
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Vulnerability Title
MIME::Field::ParamVal versions before 5.521 for Perl do not flag an ambiguous multipart boundary written as RFC 2231 continuations
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
解释冲突
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
- - 0 ~ 5.521 -

II. Public POCs for CVE-2026-116265

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-116265

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Other References for CVE-2026-116265 (1)

IV. Related Vulnerabilities

Same weakness: CWE-436