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CVE-2026-74987 covers internally found security bugs affecting Thunderbird ESR 140.13, Thunderbird ESR 153.0, and Thunderbird 153. Mozilla described the issue set as including evidence of memory corruption or another security-relevant defect and assessed that, with sufficient effort, some of the bugs could potentially be exploitable. The available information does not identify a specific vulnerable function or component for this CVE, indicating that it represents a bundled class of internally discovered defects rather than a single publicly documented root cause. The issue was addressed in Thunderbird 140.14, Thunderbird 153.1, and Thunderbird 154, with corresponding Firefox fixes also released on aligned branches.
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What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
13 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A specific vulnerability affecting Debian 13 firefox-esr packages; no further technical details are provided in the content.
A critical unpatched vulnerability tracked as CVE-2026-74987 affecting Mozilla-related packages on Ubuntu and Debian, including Firefox ESR, Thunderbird, and multiple mozjs package versions.
Unknown; listed as one of multiple vulnerabilities addressed by Mozilla Thunderbird 140.14.
A vulnerability affecting Mozilla Thunderbird, referenced by a Tenable plugin for macOS Thunderbird 140.14.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.