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CVE-2026-2766 is a use-after-free vulnerability in the JavaScript Engine JIT component used by Mozilla Firefox and Mozilla Thunderbird. The flaw arises from incorrect lifetime management of memory in JIT-compiled JavaScript handling, allowing previously freed memory to be accessed after release. In memory-unsafe contexts, this condition can lead to memory corruption and destabilization of the browser or mail client process when processing attacker-controlled script content. Mozilla fixed the issue in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository is a small, focused proof-of-concept for CVE-2026-2766 in Mozilla's JavaScript engine. It contains only two files: a README describing the bug, crash evidence, and intended exploitation path; and poc.js, a short JavaScript regression-test-style trigger. The exploit is not a remote weaponized exploit and contains no shellcode or post-exploitation payload. Its capability is to reliably exercise a JIT miscompilation / stale ICScript lifetime bug that leads to a use-after-free/use-after-move condition during compacting GC. The poc.js file primes JIT behavior by repeatedly constructing objects through Inner, Other, and outer, then sets a callback so that object construction re-enters code that changes call-site behavior. The exploit() function calls outer(Other, true), invokes gczeal(14, 1) to force compacting GC on allocation, and then calls outer(Inner, true), which is intended to trigger dereference of a stale ICScript pointer retained in the inline cache chain. The expected result on a vulnerable ASAN/fuzzing jsshell is a crash with a poisoned 0xe5... address, demonstrating memory safety corruption. There are no network callbacks, C2 endpoints, or external services contacted by the code. The only fingerprintable items are local execution artifacts and documentation references. Overall, this is a legitimate local/browser-engine crash PoC aimed at vulnerability research and exploit development, with the README explicitly stating that weaponization is still in progress.
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12 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.
No news coverage yet. Advisories and community discussion only.
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Cross-references every affected SKU, including bundled OEM variants.
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