Mozilla Firefox DOM Navigation site-isolation bypass (public exploit code, no confirmed ITW); fixed 152.0.6

Firefox 152.0.6 — chained WebAssembly memory-safety and DOM-navigation site-isolation flaws with public exploit code (CVE-2026-15718, CVE-2026-15719)

Mozilla released Firefox 152.0.6 on 2026-07-14 to fix two flaws NCSC-NL flagged on 2026-07-16 specifically because exploit code is public, which raises the likelihood of abuse (NCSC-NL, 2026-07-16). CVE-2026-15718 is an invalid-pointer memory-safety bug in the JavaScript engine's WebAssembly component; CVE-2026-15719 is a site-isolation bypass in the DOM Navigation component (Mozilla, 2026-07-14). The pairing matches the classic browser-exploit shape where a site-isolation bypass turns a memory-safety bug into cross-origin/sandbox-relevant code execution, needing only that a victim load a malicious page or a legitimate page serving a malicious ad. Severity ratings diverge across the primaries: Mozilla labels both flaws "Critical" impact, while NCSC-NL's CSAF record scores them CVSS 3.1 MEDIUM (CVE-2026-15718 base 4.3, CVE-2026-15719 base 5.4) — the individual base scores are moderate, and the operational concern is the chained code-execution potential plus the public exploit code, not a high CVSS. Crucially, Mozilla's own advisory text for both CVEs is explicit: "we are aware that exploit code for this is public however we are not aware of any attacks in the wild abusing this flaw" — so the accurate status is public PoC, not confirmed exploitation, and the "zero-day exploited in attacks" framing carried by at least one vulnerability-scanner blog overstates the primary source.