CVE-2026-6786
Reported by mozilla · Published April 21, 2026
Memory safety bugs present in Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
Fixed versions
Upgrade to a fixed version or later. Language registries are listed first, then Linux distributions, then vendor products.
| Package | Ecosystem | Fixed in |
|---|---|---|
| thunderbird-debuginfo | errata.rockylinux.org | 140.10.1-1.el9, 140.10.0-1.el9, 140.10.0-1.el8, 140.10.0-1.el10, 0:140.10.0-1.el8_10.x86_64, 0:140.10.0-1.el8_10.aarch64, 0:140.10.0-1.el10_1.x86_64, 0:140.10.0-1.el10_1.s390x, 0:140.10.0-1.el10_1.ppc64le, 0:140.10.0-1.el10_1.aarch64 |
| thunderbird | errata.rockylinux.org | 140.10.1-1.el9, 140.10.0-1.el9, 140.10.0-1.el8, 140.10.0-1.el10, 0:140.10.0-1.el8_10.x86_64, 0:140.10.0-1.el8_10.src, 0:140.10.0-1.el8_10.aarch64, 0:140.10.0-1.el10_1.x86_64, 0:140.10.0-1.el10_1.src, 0:140.10.0-1.el10_1.s390x, 0:140.10.0-1.el10_1.ppc64le |
| firefox-debuginfo | errata.rockylinux.org | 140.10.0-1.el9, 140.10.0-1.el8, 140.10.0-1.el10, 0:140.10.0-1.el9_7.x86_64, 0:140.10.0-1.el9_7.s390x, 0:140.10.0-1.el9_7.ppc64le, 0:140.10.0-1.el9_7.aarch64, 0:140.10.0-1.el8_10.x86_64, 0:140.10.0-1.el10_1.x86_64, 0:140.10.0-1.el10_1.s390x, 0:140.10.0-1.el10_1.ppc64le, 0:140.10.0-1.el10_1.aarch64 |
| firefox-debugsource | errata.rockylinux.org | 140.10.0-1.el9, 140.10.0-1.el8, 140.10.0-1.el10, 0:140.10.0-1.el9_7.x86_64, 0:140.10.0-1.el9_7.s390x, 0:140.10.0-1.el9_7.ppc64le, 0:140.10.0-1.el9_7.aarch64, 0:140.10.0-1.el8_10.x86_64, 0:140.10.0-1.el8_10.aarch64, 0:140.10.0-1.el10_1.x86_64, 0:140.10.0-1.el10_1.s390x, 0:140.10.0-1.el10_1.ppc64le, 0:140.10.0-1.el10_1.aarch64 |
| firefox | errata.rockylinux.org | 140.10.0-1.el9, 140.10.0-1.el8, 140.10.0-1.el10, 0:140.10.0-1.el9_7.x86_64, 0:140.10.0-1.el9_7.src, 0:140.10.0-1.el9_7.s390x, 0:140.10.0-1.el9_7.ppc64le, 0:140.10.0-1.el9_7.aarch64, 0:140.10.0-1.el8_10.x86_64, 0:140.10.0-1.el8_10.src, 0:140.10.0-1.el8_10.aarch64, 0:140.10.0-1.el10_1.x86_64, 0:140.10.0-1.el10_1.src, 0:140.10.0-1.el10_1.s390x, 0:140.10.0-1.el10_1.ppc64le, 0:140.10.0-1.el10_1.aarch64 |
| thunderbird-debugsource | errata.rockylinux.org | 140.10.1-1.el9, 140.10.0-1.el9, 140.10.0-1.el10, 0:140.10.0-1.el10_1.x86_64, 0:140.10.0-1.el10_1.s390x, 0:140.10.0-1.el10_1.ppc64le, 0:140.10.0-1.el10_1.aarch64 |
| firefox | Wolfi | 140.10-r0 |
| firefox-x11 | errata.rockylinux.org | 140.10.0-1.el9, 0:140.10.0-1.el9_7.s390x, 0:140.10.0-1.el9_7.ppc64le, 0:140.10.0-1.el9_7.aarch64 |
| firefox | Chainguard | 140.10-r0 |
| firefox | Amazon Linux | 140.10.1-1.amzn2023.0.1 |
| thunderbird | Amazon Linux | 140.10.0-1.amzn2.0.1 |
| firefox-esr | Chainguard | 140.10-r0, 140.10.1-r0 |
2 more packages have a fixed version. See every fix in Lookup.
Risk scores
Affected products
| Vendor | Product | Versions |
|---|---|---|
| Mozilla | Firefox | 140.10, 150 |
| Mozilla | Thunderbird | 140.10, 150 |
| Mozilla | Firefox | 150, 140.10 |
| Mozilla | Thunderbird | 140.10, 150 |
Timeline
- Apr 21, 2026 CVE Published
- Apr 22, 2026 EPSS Score (30 in total, the first dated here)
- Apr 27, 2026 Distribution Patch (37 in total, the first dated here)
- Apr 27, 2026 Security Advisory (34 in total, the first dated here)
- Jul 14, 2026 Coalition ESS Score
Query this with the API
The same record, from the CLI:
vulnetix vdb vuln CVE-2026-6786
vulnetix vdb fixes CVE-2026-6786Or with curl, using the org id and key from your account page:
curl -s -H "Authorization: ApiKey ${VULNETIX_ORG_ID}:${VULNETIX_API_KEY}" \
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