CVE-2026-6755: Mitigation bypass in the DOM: postMessage component
Mitigation bypass in the DOM: postMessage component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 150 - Upgrade
Upgrade
Firefoxto a version that resolves this vulnerability.Fixed in 150 - Upgrade
Upgrade
Thunderbirdto a version that resolves this vulnerability.Fixed in 150
Event History
Peer vulnerabilities
Found alongside the following vulnerabilities.
- CVE-2026-6746
- CVE-2026-6747
- CVE-2026-6748
- CVE-2026-6749
- CVE-2026-6750
- CVE-2026-6751
- CVE-2026-6752
- CVE-2026-6753
- CVE-2026-6754
- CVE-2026-6755
- CVE-2026-6757
- CVE-2026-6758
- CVE-2026-6759
- CVE-2026-6760
- CVE-2026-6761
- CVE-2026-6762
- CVE-2026-6763
- CVE-2026-6764
- CVE-2026-6765
- CVE-2026-6766
- CVE-2026-6767
- CVE-2026-6768
- CVE-2026-6769
- CVE-2026-6770
- CVE-2026-6771
- CVE-2026-6772
- CVE-2026-6773
- CVE-2026-6774
- CVE-2026-6775
- CVE-2026-6776
- CVE-2026-6777
- CVE-2026-6778
- CVE-2026-6779
- CVE-2026-6780
- CVE-2026-6781
- CVE-2026-6782
- CVE-2026-6783
- CVE-2026-7321
- CVE-2026-8091
- CVE-2026-6784
- CVE-2026-6785
- CVE-2026-6786
- CVE-2026-6756
Frequently Asked Questions
What is the severity of CVE-2026-6755?
The severity of CVE-2026-6755 is medium with a CVSS score of 6.5.
How do I fix CVE-2026-6755?
To fix CVE-2026-6755, update Mozilla Firefox and Thunderbird to version 150 or later.
What type of vulnerability is CVE-2026-6755?
CVE-2026-6755 is categorized as a mitigation bypass vulnerability in the postMessage component of the DOM.
Is CVE-2026-6755 a critical vulnerability?
CVE-2026-6755 is not a critical vulnerability; it has a medium severity rating.
When was CVE-2026-6755 published?
CVE-2026-6755 was published on April 21, 2026.