bytecodealliance
Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation
Not on CISA's list of exploited flaws, and not in the news we track.
CVE-2026-115889Critical9.9
Black Shard's team can check your exposure to CVE-2026-115889 and take the fix off your plate.
Wasmtime is a runtime for WebAssembly. Prior to 36.0.19 and 43.0.0, the Cranelift compiler backend bit-packs SSA value indices in a way that can silently overflow in release builds when compiling a sufficiently large or specially crafted Wasm function with many SSA values. The overflow can make Cranelift reference incorrect IR values, causing arbitrary miscompilation, type confusion, and other attacker-controlled effects that may escape the Wasm sandbox on any architecture using the default Cranelift backend. This issue is fixed in versions 36.0.19 and 43.0.0.
Black Shard's team can check your exposure, take a fix off your plate or step in on a live incident.
Chance of exploitation in the next 30 days
0.45%
EPSS score from FIRST
Updated 13 Nov 2026, 12:00 UTC, 30 of 36 sources answering.
CISA Known Exploited Vulnerabilities, NVD, CVE.org, CIRCL Vulnerability-Lookup, GitHub Advisory Database (CC BY 4.0), OSV (CC BY 4.0), RansomLook (CC BY 4.0, enriched by Black Shard), SEC EDGAR, HHS breach portal, Have I Been Pwned (CC BY 4.0), Texas Attorney General, California Attorney General, Delaware Department of Justice, Vermont Attorney General, GDELT Project, Cloudflare status, abuse.ch SSLBL (CC0), CISA ICS advisories, NCSC UK (OGL v3.0), CERT-EU (CC BY 4.0), NCSC New Zealand (CC BY 4.0), MISP galaxy (CC0), OAIC determinations (CC BY 4.0), abuse.ch Feodo Tracker (CC0), Spamhaus DROP (Spamhaus DROP terms), blocklist.de, CINS Army, CERT-FR (Licence Ouverte 2.0), Red Hat Security Data (CC BY 4.0), ENISA EUVD, Microsoft MSRC, JVN iPedia, FIRST EPSS, IODA, GeoNames (CC BY 4.0), Natural Earth, Wikidata, Regional Internet Registries (delegation statistics), Protomaps, OpenStreetMap contributors (ODbL), NASA GIBS. Items link to their sources, except leak-site claims, which are never linked. This product uses the NVD API but is not endorsed or certified by the NVD.
Built on open-source software under the MIT licence. Map data from Natural Earth, NASA GIBS, Protomaps and OpenStreetMap contributors.
© 2026 Black Shard Pty LtdABN 66 696 910 773