CVE-2026-34983: bytecodealliance wasmtime Use After Free
Vulnerability summary
CVE-2026-34983 is a medium (CVSS 5.0) Use After Free vulnerability in bytecodealliance wasmtime. EPSS estimates a 0.12% chance of exploitation in the next 30 days, higher than 1.5% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 0 · Related 1Timeline
- 09-04-2026PublishedVulnerability first disclosed.
- 13-04-2026Last modifiedVulnerability information updated.
Description
Wasmtime is a runtime for WebAssembly. In 43.0.0, cloning a wasmtime::Linker is unsound and can result in use-after-free bugs. This bug is not controllable by guest Wasm programs. It can only be triggered by a specific sequence of embedder API calls made by the host. Specifically, the following steps must occur to trigger the bug clone a wasmtime::Linker, drop the original linker instance, use the new, cloned linker instance, resulting in a use-after-free. This vulnerability is fixed in 43.0.1.
CVSS metrics
10 scores · 8 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated1.0LowCVSS:4.0/AV:P/AC:H/AT:P/PR:H/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N
- OSV · WolfiEcosystem advisory · calculated1.0LowCVSS:4.0/AV:P/AC:H/AT:P/PR:H/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N
- OSV · ChainguardEcosystem advisory · calculated1.0LowCVSS:4.0/AV:P/AC:H/AT:P/PR:H/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N
- OSV · Crates.ioEcosystem advisory · calculated1.0LowCVSS:4.0/AV:P/AC:H/AT:P/PR:H/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N
- NVDNIST1.0LowCVSS:4.0/AV:P/AC:H/AT:P/PR:H/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- OSV · PypiEcosystem advisory · calculated5.0MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
- OSV · UbuntuEcosystem advisory · calculated5.0MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated5.0MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.12%
Chance of exploitation in the next 30 days
Percentile
2%
Versus all other CVEs
30-day change
0.00 pp
From 0.12% on 20-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Bytecodealliance1 product
- wasmtime≥ 43.0.0, < 43.0.1 | 43.0.0
Chainguard1 product
- wasmcloud< 2.0.4-r0
Crates.Io1 product
- wasmtime≥ 43.0.0, < 43.0.1
Debian1 product
- rust-wasmtimeAll versions (No fix recorded) | < 36.0.7+dfsg-1
PyPI1 product
- wasmtime≤ 43.0.0
Ubuntu1 product
- rust-wasmtimeAll versions (No fix recorded)
Wolfi1 product
- wasmcloud< 2.0.4-r0
7 vendors · 7 products
References
11 links- github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hfr4-7c6c-48w2X Refsource CONFIRMAdvisoryREPORTWEBMitigationVendor Advisory
- crates.io/crates/wasmtimePACKAGE