VulnerabilityPublished 28 Oct 2026

CVE-2026-116269: MIME::Field::ParamVal versions before 5.521 for Perl turn an RFC 2231 filename with a hyphenated

Source GCVE Database

Authoritative record:CVE-2026-116269· Medium

Not known to be exploited : upgrade to 5.521 when convenient.

Data as of 28 Oct 2026, 19:30 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · CVSS not yet scored by NVD

Patch: Available – fixed in 5.521

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-h2xx-9xmf-ppmv

What to do

Upgrade MIME-tools (Perl module) to 5.521.

Affected software

Product	Affected	Fixed in
MIME-tools	Affected <5.521	Fixed in 5.521
CPANMIME-tools`pkg:cpan/MIME-tools`Other threats	Affected <5.521	Fixed in 5.521

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, users should be aware of this parsing issue and consider additional controls beyond relying solely on recommended filename extension checks.

Description

MIME::Field::ParamVal versions before 5.521 for Perl incorrectly handle RFC 2231 filenames with hyphenated language tags, resulting in an empty recommended filename. This occurs because the decoder fails to strip the language suffix when it contains hyphens, causing the recommended_filename() method to return an empty string instead of the actual filename. This behavior differs from other mail readers that correctly return the filename. Consequently, a remote sender can bypass file extension checks on the recommended filename, potentially allowing disallowed attachments to be delivered.

Impact

A remote attacker can exploit this vulnerability to bypass file extension-based security policies by sending attachments with filenames encoded using RFC 2231 with hyphenated language tags. The affected software returns an empty recommended filename, which may cause security controls to fail to detect or block disallowed file types. This could lead to delivery of potentially malicious attachments that are normally restricted.

Summary

The vulnerability in MIME::Field::ParamVal versions prior to 5.521 for Perl involves improper parsing of RFC 2231 encoded filenames that include hyphenated language tags (e.g., 'utf-8'en-US'payload.exe'). The decoder appends the language tag to the charset but only strips the language suffix if it is a single word. Because 'en-US' is hyphenated, the decoder cannot resolve the charset correctly and returns an empty string. The recommended_filename() method then returns this empty string instead of falling back to the original filename parameter. This flaw allows a remote sender to circumvent file extension policies that rely on the recommended filename, potentially enabling delivery of attachments that would otherwise be blocked.

CWE-436Interpretation Conflict (opens in a new tab)
Class weaknessOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B's state.
OWASP Cheat Sheets
REST Assessment (opens in a new tab)
REST Security (opens in a new tab)
Cross-Site Request Forgery Prevention (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V13.2.5 (opens in a new tab)
Attack patterns
HTTP Request Splitting (opens in a new tab)
HTTP Response Smuggling (opens in a new tab)
HTTP Response Splitting (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 28 Oct 2026, 19:30 UTC

WeaknessesCWE-436

Technical details

References

Community reviews

Related threats