| Name | CVE-2026-5734 |
| Description | Memory safety bugs present in Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. 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 149.0.2, Firefox ESR 140.9.1, Thunderbird 149.0.2, and Thunderbird 140.9.1. |
| Source | CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) |
| References | DLA-4526-1, DLA-4534-1, DSA-6202-1, DSA-6211-1 |
The table below lists information on source packages.
| Source Package | Release | Version | Status |
|---|---|---|---|
| firefox (PTS) | sid | 150.0-1 | fixed |
| firefox-esr (PTS) | bullseye | 115.14.0esr-1~deb11u1 | vulnerable |
| bullseye (security) | 140.10.0esr-1~deb11u1 | fixed | |
| bookworm | 128.14.0esr-1~deb12u1 | vulnerable | |
| bookworm (security) | 140.10.0esr-1~deb12u1 | fixed | |
| trixie | 140.8.0esr-1~deb13u1 | vulnerable | |
| trixie (security) | 140.10.0esr-1~deb13u1 | fixed | |
| forky, sid | 140.10.0esr-1 | fixed | |
| thunderbird (PTS) | bullseye | 1:115.12.0-1~deb11u1 | vulnerable |
| bullseye (security) | 1:140.10.0esr-1~deb11u1 | fixed | |
| bookworm | 1:140.6.0esr-1~deb12u1 | vulnerable | |
| bookworm (security) | 1:140.10.0esr-1~deb12u1 | fixed | |
| trixie | 1:140.8.0esr-1~deb13u1 | vulnerable | |
| trixie (security) | 1:140.10.0esr-1~deb13u1 | fixed | |
| forky, sid | 1:140.10.0esr-1 | fixed |
The information below is based on the following data on fixed versions.
| Package | Type | Release | Fixed Version | Urgency | Origin | Debian Bugs |
|---|---|---|---|---|---|---|
| firefox | source | (unstable) | 149.0.2-1 | |||
| firefox-esr | source | bullseye | 140.9.1esr-1~deb11u1 | DLA-4526-1 | ||
| firefox-esr | source | bookworm | 140.9.1esr-1~deb12u1 | DSA-6202-1 | ||
| firefox-esr | source | trixie | 140.9.1esr-1~deb13u1 | DSA-6202-1 | ||
| firefox-esr | source | (unstable) | 140.9.1esr-1 | |||
| thunderbird | source | bullseye | 1:140.9.1esr-1~deb11u1 | DLA-4534-1 | ||
| thunderbird | source | bookworm | 1:140.9.1esr-1~deb12u1 | DSA-6211-1 | ||
| thunderbird | source | trixie | 1:140.9.1esr-1~deb13u1 | DSA-6211-1 | ||
| thunderbird | source | (unstable) | 1:140.9.1esr-1 |
https://www.mozilla.org/en-US/security/advisories/mfsa2026-25/#CVE-2026-5734
https://www.mozilla.org/en-US/security/advisories/mfsa2026-27/#CVE-2026-5734
https://www.mozilla.org/en-US/security/advisories/mfsa2026-29/#CVE-2026-5734