Integer overflow in libmime buffer growth can corrupt heap memory
Key facts
- Attack vector
- Local
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Partial Red Hat: 5 without a fix
Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA and Red Hat. Impact type from CWE-190 and the CVSS impact.
Summary
Mozilla Thunderbird's libmime performs buffer-size arithmetic in 32-bit types without overflow checks (CWE-190). On a sufficiently large message, the growth guard can fail open or the buffer can be reallocated smaller than required, so a later memcpy writes attacker-controlled data across adjacent heap allocations. A local user with no privileges can trigger this without user interaction.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Description from the CNA
Several buffer-growth sites in libmime performed size arithmetic in 32-bit types without overflow checks. On a sufficiently large message the growth guard could fail open, or the buffer could be reallocated smaller than required, and a subsequent memcpy would then write attacker-controlled data across adjacent heap allocations. This vulnerability was fixed in Thunderbird 158 and Thunderbird 153.6.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
Update Mozilla Thunderbird to version 153.6 or 158, which fix this flaw. The sources list no fixed version for Red Hat Enterprise Linux 8, 9 and 10, and no fix planned for Red Hat Enterprise Linux 6 and 7.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
- Fix · CNA Thunderbird (Mozilla) Fixed in 153.6, 158
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 8 | Affected | No fix yet |
| Red Hat Enterprise Linux 9 | Affected | No fix yet |
Timeline
- 2026-10-13 Threatist record created from CVE-2026-110247
- 2026-10-13 Alias added: GHSA-6c5g-4xv7-7fmm
- 2026-10-15 Affected versions changed · Red Hat
- 2026-10-15 CVSS score added · Red Hat
- 2026-10-20 CVSS score added · CISA ADP
- 2026-10-20 Weakness changed · CISA ADP
- 2026-10-20 CISA SSVC decision points changed
- 2026-10-27 Fix available: Mozilla/[email protected] · CNA
- 2026-10-27 1 new reference · CNA
- 2026-10-30 Affected versions changed · Red Hat
- 2026-10-30 CVSS score changed · Red Hat
- 2026-10-30 Affected versions changed · Red Hat
- 2026-11-02 Affected versions changed · Red Hat
- 2026-11-06 Affected versions changed · Red Hat
References
More Mozilla vulnerabilities
- TI-2024-08981 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.8
- TI-2022-09832 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.6
- TI-2019-08769 Improper input validation in Mozilla Firefox ESR KEVCVSS 3.1CRITICAL 10.0
- TI-2010-03577 Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before… KEVCVSS 3.1CRITICAL 9.8
- TI-2023-04799 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
- TI-2023-04477 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
Sources
- CVE-2026-110247 · CVE Program
- CVE-2026-110247 · NVD
- FIRST EPSS
- GHSA-6c5g-4xv7-7fmm · GitHub Advisory Database · CC BY 4.0
- CVE-2026-110247 · 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