Vulnerability · CVE-2026-109776
Race condition in the XPCOM component.
Published Oct 13, 2026 · catalog updated Oct 15, 2026 · Race condition in the
Check if you run it
No confirmed exploitation is on record for CVE-2026-109776. EPSS is 0.14%. Act only if a listed version of Race condition in the is installed.
Gaps on this record
- The stored product name is a package slug. The name on this page is taken from the title (Race condition in the).
- 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
- 0.14%
- Remediation
- Advisory link
- Affected products
- Debian:12 firefox-esr · Debian:12 thunderbird · Debian:13 firefox-esr · Debian:13 thunderbird · Debian:14 firefox-esr · Debian:14 thunderbird
Race condition in the XPCOM component. This vulnerability was fixed in Firefox 158, 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.
- Debian:12 firefox-esr0 → 153.5.0esr-1~deb12u1
- Debian:12 thunderbird1:102.11.0-1, 1:102.12.0-1, 1:102.12.0-1~deb10u1
- Debian:13 firefox-esr0 → 153.5.0esr-1~deb13u1
- Debian:13 thunderbird1:128.13.0esr-1, 1:128.14.0esr-1, 1:128.14.0esr-1~deb11u1
- Debian:14 firefox-esr128.13.0esr-1, 128.14.0esr-1, 128.14.0esr-1~deb11u1
- Debian:14 thunderbird1:128.13.0esr-1, 1:128.14.0esr-1, 1:128.14.0esr-1~deb11u1
How to fix CVE-2026-109776
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-2026-109776. EPSS is 0.14%. Act only if a listed version of Race condition in the is installed.
Which versions are affected?
Compare what you have installed with 0 → 153.5.0esr-1~deb12u1, 1:102.11.0-1, 1:102.12.0-1, 1:102.12.0-1~deb10u1, 0 → 153.5.0esr-1~deb13u1, 1:128.13.0esr-1, 1:128.14.0esr-1, 1:128.14.0esr-1~deb11u1, 128.13.0esr-1, 128.14.0esr-1, 128.14.0esr-1~deb11u1. Compare the installed version with the linked vendor advisory before you change production.
What should an analyst verify?
No weakness class is stored. EPSS 0.14%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Technology hubs
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 · OpenSSF OSV / OSV Scanner
Detected
Race condition in the XPCOM component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
Oct 15, 2026 · OpenSSF OSV / OSV Scanner
Fix available
firefox-esr fixed in 153.5.0esr-1~deb12u1; firefox-esr fixed in 153.5.0esr-1~deb13u1
Oct 15, 2026 · OpenSSF OSV / OSV Scanner
Fix available
firefox-esr fixed in 153.5.0esr-1~deb12u1
Oct 15, 2026 · OpenSSF OSV / OSV Scanner
Fix available
firefox-esr fixed in 153.5.0esr-1~deb13u1
Oct 15, 2026 · OpenSSF OSV / OSV Scanner
Updated
Race condition in the XPCOM component. This vulnerability was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
Sources
- CVE.orgVulnerability recordCVE-2026-109776
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2026-109776
30-day exploitation probability 0.1%
first.org - Mozilla Security AdvisoriesVendor advisoryCVE-2026-109776
Security Vulnerabilities fixed in Thunderbird 153.5 — Mozilla
mozilla.org - OpenSSF OSV / OSV ScannerPackage advisoryDEBIAN-CVE-2026-109776osv.dev
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.