What’s Vulnerable › Vulnerabilities

CVE-2026-115381: Wasmtime before 36.0.17, 37.0.0 before 48.0.4, and 49.0.0 before 49.0.2 Unbounded Host Memory Allocation via SinkOutputStream write-zeroes

• Severity: medium (CVSS 4.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-22 · updated 2026-10-26
• Weakness: CWE-770

Description

Wasmtime before 36.0.17, 37.0.0 before 48.0.4, and 49.0.0 before 49.0.2 contains an unbounded memory allocation in the wasmtime-wasi WASIp2 write-zeroes method of SinkOutputStream, the default stream used when stdout/stderr are not configured. A malicious WebAssembly guest can request huge zero-filled writes, exhausting host memory and causing denial of service.

Affected products

• bytecodealliance wasmtime: before 36.0.17; from 37.0.0 before 48.0.4; from 49.0.0 before 49.0.2 — fixed in 36.0.17, 48.0.4, 49.0.2

How to fix

Upgrade to a fixed version: bytecodealliance wasmtime 36.0.17, 48.0.4, 49.0.2. Check the vendor advisory for mitigations.

References

• https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-gqmc-89g8-p25r
• https://www.vulncheck.com/advisories/wasmtime-before-36.0.17-37.0.0-before-48.0.4-and-49.0.0-before-49.0.2-unbounded-host-memory-allocation-via-sinkoutputstream-write-zeroes

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