How severe is CVE-2026-34983?

CVE-2026-34983 has a CVSS 3.x base score of 5.0, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-34983 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (2nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34983?

CVE-2026-34983 affects Bytecodealliance Wasmtime. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34983?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-34983 have an EU (EUVD) identifier?

Yes. CVE-2026-34983 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-21029.

When was CVE-2026-34983 published?

CVE-2026-34983 was published on 2026-04-09 and last updated on 2026-06-17.

CVE-2026-34983

CVE-2026-34983 is a medium-severity vulnerability in Bytecodealliance Wasmtime with a CVSS 3.x base score of 5.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-416.

Key facts

Severity: Medium (CVSS 3.x base score 5.0)
CVSS v4: 1.0
EPSS exploit prediction: 0% (2nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-21029
Weakness: CWE-416
Affected product: Bytecodealliance Wasmtime
Published: 2026-04-09
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-34983?: 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.
How severe is CVE-2026-34983?: CVE-2026-34983 has a CVSS 3.x base score of 5.0, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-34983 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (2nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34983?: CVE-2026-34983 affects Bytecodealliance Wasmtime. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34983?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-34983 have an EU (EUVD) identifier?: Yes. CVE-2026-34983 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-21029.
When was CVE-2026-34983 published?: CVE-2026-34983 was published on 2026-04-09 and last updated on 2026-06-17.

References

https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hfr4-7c6c-48w2

Affected products (1)

cpe:2.3:a:bytecodealliance:wasmtime:43.0.0:*:*:*:*:rust:*:*

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Other CWE-416 (Use After Free) vulnerabilities

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CVE-2025-24085 — Critical (CVSS 10.0): A use after free issue was addressed with improved memory management. This issue is fixed in iOS 18.3 and iPadOS 18.3,…
CVE-2024-43102 — Critical (CVSS 10.0): Concurrent removals of certain anonymous shared memory mappings by using the UMTX_SHM_DESTROY sub-request of…
CVE-2021-32495 — Critical (CVSS 10.0): Radare2 has a use-after-free vulnerability in pyc parser's get_none_object function. Attacker can read freed memory…

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