Vulnerability · CVE-2026-109753
Incorrect boundary conditions in the Layout component
Published Oct 13, 2026 · catalog updated Oct 15, 2026 · Mozilla Firefox
Check if you run it
No confirmed exploitation is on record for CVE-2026-109753. EPSS is 0.34%. Act only if a listed version of Mozilla Firefox is installed.
Gaps on this record
- No version range is stored. A customer cannot check an installed version against this record.
- No vendor fix or required action is stored. Compare the linked advisory before you change production.
- Severity
- Unknown—
- Known exploitation
- Not in CISA/VulnCheck KEV
- EPSS
- 0.34%
- Remediation
- Advisory link
- Affected products
- vendor Mozilla Firefox · vendor Mozilla Thunderbird
Incorrect boundary conditions in the Layout component. This vulnerability was fixed in Firefox 158, Firefox ESR 115.43, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
Are you affected?
Enter the version you run. The result uses only the ranges stored on this record.
The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.
- vendor Mozilla Firefoxversion unspecified
- vendor Mozilla Thunderbirdversion unspecified
How to fix CVE-2026-109753
Recommended remediation
A patch or advisory reference is linked. Open the original publisher for availability by product version.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
No confirmed exploitation is on record for CVE-2026-109753. EPSS is 0.34%. Act only if a listed version of Mozilla Firefox is installed.
Which versions are affected?
Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.
What should an analyst verify?
No weakness class is stored. EPSS 0.34%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Oct 13, 2026 · CIRCL Vulnerability Lookup
Detected
Incorrect boundary conditions in the Layout component. This vulnerability was fixed in Firefox 158, Firefox ESR 115.43, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
Oct 15, 2026 · CIRCL Vulnerability Lookup
Updated
Incorrect boundary conditions in the Layout component. This vulnerability was fixed in Firefox 158, Firefox ESR 115.43, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
Sources
- CIRCL Vulnerability LookupVulnerability recordCVE-2026-109753
Incorrect boundary conditions in the Layout component. This vulnerability was fixed in Firefox 158, Firefox ESR 115.43, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
vulnerability.circl.lu - CVE.orgVulnerability recordCVE-2026-109753
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2026-109753
30-day exploitation probability 0.3%
first.org - Mozilla Security AdvisoriesVendor advisoryCVE-2026-109753
Security Vulnerabilities fixed in Thunderbird 153.5 — Mozilla
mozilla.org
References
Freshness
Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.