Skip to main content
No exploitation reportedFix availableAwaiting NVD analysis

CVE-2026-116266

MIME::Head versions from 5.518 before 5.521 for Perl decode a partly encoded multipart boundary without flagging the parse as ambiguous

No exploitation reported by the sources we read.

  • Published2026-10-28
  • WeaknessCWE-436

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC
  1. 2026-10-2817:32CVE publishedCNA

Versions per branch

Products declared by the CNA1 product

As CPANSec, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-10-28

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • libmime-tools-perlUbuntu:26.10all versions · no fixed version listed
  • libmime-tools-perlUbuntu:26.04:LTSall versions · no fixed version listed
  • libmime-tools-perlUbuntu:24.04:LTSall versions · no fixed version listed
  • libmime-tools-perlUbuntu:22.04:LTSall versions · no fixed version listed
  • libmime-tools-perlUbuntu:20.04:LTSall versions · no fixed version listed
  • libmime-tools-perlUbuntu:18.04:LTSall versions · no fixed version listed
  • libmime-tools-perlUbuntu:16.04:LTSall versions · no fixed version listed
  • libmime-tools-perlUbuntu:14.04:LTSall versions · no fixed version listed

5 more package ranges on OSV.dev

Vendor advisories

  • CVE-2026-116266 Red Hat Product Security1 known affected

    perl-mime-tools: perl-mime-tools: Security filter bypass via partially encoded multipart boundary

    perl-MIME-tools.src as a component of Red Hat Enterprise Linux 6

Full record on NVD

Fix

  1. No fix planned, says the vendor Red Hat Product Security CVE-2026-116266 · 1 productOut of support scope

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Published
2026-10-28
Last Modified
2026-11-05
NVD status
Awaiting Analysis
GitHub Advisory
GHSA-c5m8-q98x-42wx

Frequently asked questions

What is CVE-2026-116266?

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.

Is CVE-2026-116266 actively exploited?

Active exploitation of CVE-2026-116266 has not been confirmed. Its EPSS score was 0.2% on 2026-11-05, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-116266?

CVE-2026-116266 has a CVSS v3 base score of 5.3 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.

Running perl-mime-tools? Hear about its next vulnerability

Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».

Get alerts for this productCISA KEV additions, November 2026Search CVEs

No credit card required · No monthly cap on website lookups · 250 API requests/month

Go further

Related vulnerabilities

Same product first, then the same vendor advisory and the same publication week.

Back to CVE Database

Sources for this record