MIME-tools misses duplicate boundary parameters with nested comments
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · Low · None
- Fix status
- Partial Red Hat: 1 without a fix
Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA and Red Hat.
Summary
MIME-tools versions before 5.521 for Perl do not flag a duplicate boundary parameter whose name contains a nested comment. The parser stores such a parameter under a literal name, so MIME::Parser splits the message on a second boundary that is not reported as a duplicate (CWE-436). A remote sender with no privileges and no user interaction can hide an attachment from a filter that relies on ambiguous_content() while the recipient's mail client shows it.
Written with Claude Haiku 5.5 from the sources below · 2026-11-05
Description from the CNA
MIME::Field::ParamVal versions before 5.521 for Perl do not flag a duplicate boundary parameter whose name contains a nested comment. A parameter written boundary((c))="A" or boundary(\))="A" is stored under that literal name rather than as boundary. A second boundary parameter is then not reported as a duplicate, and MIME::Parser splits the message on it. Readers that skip comments as RFC 5322 allows take the first boundary instead. A remote sender can hide an attachment from a filter that relies on ambiguous_content() while the recipient's mail client shows it.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | MIME-tools | before 5.521 | 5.521 | Patch available | CNA |
- MIME-tools Vendor— Affected before 5.521 Fixed in 5.521 Patch available CNA
Remediation
Upgrade MIME-tools to version 5.521, which fixes this flaw. Red Hat lists Red Hat Enterprise Linux 6 as affected with no fix planned.
Written with Claude Haiku 5.5 from the sources below · 2026-11-05
- Fix · CNA MIME-tools Fixed in 5.521
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
Timeline
- 2026-10-28 Threatist record created from CVE-2026-116272
- 2026-10-28 Alias added: GHSA-hx8x-4mjr-grc3
- 2026-10-30 Affected versions changed · Red Hat
- 2026-10-30 CVSS score added · Red Hat
- 2026-11-05 CVSS score added · CISA ADP
- 2026-11-05 CISA SSVC decision points changed
References
Sources
- CVE-2026-116272 · CVE Program
- CVE-2026-116272 · NVD
- FIRST EPSS
- GHSA-hx8x-4mjr-grc3 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-116272 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences