Mozilla Firefox CVE-2026-109727

Exploitation requires the victim to actively load attacker-controlled audio/video content in an unpatched Firefox or Firefox ESR instance - i.e., visiting a malicious or compromised web page that serves crafted media (CVSS UI:R). No authentication is required (PR:N) and the attack is network-delivered (AV:N), but the mandatory user interaction and the need for the victim to run a vulnerable version (prior to Firefox 158, ESR 115.43, or ESR 153.5) are the key limiting factors. There is no indication of a non-default configuration requirement; the A/V processing path is standard browser functionality. Realistic risk is further bounded by SSVC Automatable=no, meaning the attack cannot be reliably mass-automated.

This is a moderate-severity memory-safety flaw (CVSS 5.4, CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N) whose signals consistently point to low real-world urgency rather than an emergency. The CVSS vector describes network-reachable, unauthenticated exploitation but explicitly requires user interaction (UI:R) - the victim must load attacker-controlled audio/video content - which meaningfully caps mass-exploitation potential. CISA's SSVC framework reinforces this: Exploitation=none (no observed activity), Automatable=no (cannot be reliably scripted at scale, consistent with the UI:R requirement), and Technical Impact=partial (matching the C:L/I:L/A:N limited-impact rating). There is no CISA KEV listing and no public exploit code identified at time of analysis, and no EPSS score was provided in the input, so exploitation probability cannot be quantified from this data. The impact profile (C:L/I:L, A:N) together with the 'Information Disclosure' and 'Use After Free' tags suggests the realistic worst case is reading out-of-bounds memory (e.g., leaking memory contents to aid a broader exploit chain) rather than straightforward remote code execution - though as a use-after-free (CWE-416) it is a potential building block that could be chained with other bugs. Net assessment: a genuine but non-priority browser bug - patch in the normal cycle; it is a moderate-CVSS, low-real-risk issue absent evidence of exploitation.

An attacker hosts a malicious web page containing specially crafted audio/video content and lures a victim running an unpatched Firefox build into visiting it. Loading the media triggers the use-after-free in the Audio/Video component, allowing the attacker to read leaked memory contents (limited confidentiality/integrity impact) and potentially use the freed-object condition as a step toward a larger exploit chain. No public proof-of-concept or exploit code was identified at time of analysis.