Memory exhaustion in MIME-tools for Perl via repeated encoded-word markers
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 1 without a fix
Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA and Red Hat. Impact type from CWE-407.
Summary
MIME-tools versions before 5.521 for Perl allow memory exhaustion through repeated "=?" sequences in decode_mimewords. For each "=?" that does not start a complete encoded word, the function appends an error message containing the whole input string, so a boundary of 8,000 pairs adds 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, without authentication.
Written with Claude Haiku 5.5 from the sources below · 2026-11-05
Description from the CNA
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.
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
MIME-tools fixes this in version 5.521. Red Hat Enterprise Linux 6 is affected with no fix available yet.
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: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 6 | Affected | No fix yet |
Timeline
- 2026-10-28 Threatist record created from CVE-2026-116270
- 2026-10-28 Alias added: GHSA-jq2x-c3x3-gv8c
- 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-2026-116270 · CVE Program
- CVE-2026-116270 · NVD
- FIRST EPSS
- GHSA-jq2x-c3x3-gv8c · GitHub Advisory Database · CC BY 4.0
- CVE-2026-116270 · 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