Denial of service in Thunderbird Exchange email component
Key facts
- Attack vector
- Local
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- Denial of service
- 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-400.
Summary
Mozilla Thunderbird's Exchange email component can be made to consume excessive CPU. A malicious, compromised, or man-in-the-middle Exchange server can return one well-formed SOAP response with an element carrying enough attributes to keep the main thread busy for seconds to hours, an uncontrolled resource consumption flaw (CWE-400). An attacker who controls or intercepts the Exchange server can make Thunderbird unresponsive, and the user must interact with the application to trigger it.
Written with Claude Haiku 5.5 from the sources below · 2026-10-27
Description from the CNA
A malicious, compromised, or MITM-controlled Exchange server can return a single well-formed SOAP response containing an element with enough attributes to keep Thunderbird's main thread CPU-bound for seconds to hours. This vulnerability was fixed in Thunderbird 158 and Thunderbird 153.5.
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 Thunderbird to version 153.5 or 158, which fix the flaw. The sources list no fixed version for Red Hat Enterprise Linux 6 and 7, where no fix is planned, or for Red Hat Enterprise Linux 8, 9 and 10, where none is available.
Written with Claude Haiku 5.5 from the sources below · 2026-10-27
- Fix · CNA Thunderbird (Mozilla) Fixed in 153.5, 158
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| 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: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
Not affected: 1 product
- Red Hat Enterprise Linux 10
Timeline
- 2026-10-13 Threatist record created from CVE-2026-110249
- 2026-10-13 Alias added: GHSA-3vgg-r2jh-qqpj
- 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
- 2026-10-23 Affected versions changed · Red Hat
- 2026-10-23 CVSS score changed · Red Hat
- 2026-11-03 Affected versions changed · Red Hat
References
More Mozilla vulnerabilities
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- 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-2026-110249 · CVE Program
- CVE-2026-110249 · NVD
- FIRST EPSS
- GHSA-3vgg-r2jh-qqpj · GitHub Advisory Database · CC BY 4.0
- CVE-2026-110249 · 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