Is CVE-2026-34988 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-34988 being exploited in the wild.

How severe is CVE-2026-34988?

Medium severity, with a CVSS score of 6.3, published 9 April 2026.

Which products and versions are affected?

wasmtime (crates.io) SEMVER:introduced=0.0.0-0,fixed=36.0.7,introduced=37.0.0,fixed=42.0.2,introduced=43.0.0,fixed=43.0.1, SEMVER:introduced=28.0.0,fixed=36.0.7.

Is there a fix for CVE-2026-34988?

Yes. wasmtime (crates.io): upgrade to 36.0.7, 43.0.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-34988 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-34988?

Check whether you run Bytecodealliance Wasmtime or wasmtime (crates.io) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-34988: Bytecode Alliance Wasmtime data leakage in pooling allocator

CVE-2026-34988 · Severity: medium · CVSS 6.3 · Published 2026-04-09

Wasmtime is a runtime for executing WebAssembly code in a secure, isolated environment. A bug in its memory management system can allow one guest program to access the private memory of a previously running program under specific configurations. This could lead to sensitive data leakage between different users or applications sharing the same infrastructure.

Technologies: Bytecodealliance Wasmtime, wasmtime (crates.io). Vendors: Bytecodealliance, crates.io.

Quick answers

Is CVE-2026-34988 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-34988 being exploited in the wild.
How severe is CVE-2026-34988?: Medium severity, with a CVSS score of 6.3, published 9 April 2026.
Which products and versions are affected?: wasmtime (crates.io) SEMVER:introduced=0.0.0-0,fixed=36.0.7,introduced=37.0.0,fixed=42.0.2,introduced=43.0.0,fixed=43.0.1, SEMVER:introduced=28.0.0,fixed=36.0.7.
Is there a fix for CVE-2026-34988?: Yes. wasmtime (crates.io): upgrade to 36.0.7, 43.0.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-34988 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-34988?: Check whether you run Bytecodealliance Wasmtime or wasmtime (crates.io) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

wasmtime (crates.io): upgrade to 36.0.7, 43.0.1 or later
```
cargo update -p wasmtime
```

Technical details

A logic error in Wasmtime's pooling allocator causes a divergence between runtime memory resetting and compile-time assumptions. Specifically, the allocator may use an incorrect predicate to determine if virtual memory permissions need to be reset when a linear memory slot is reused. If the pooling allocator is active, memory guard size is 0, and memory reservation is less than 4GiB (matching max_memory_size), the system fails to trigger a segfault on out-of-bounds loads. This allows a subsequent WebAssembly instance to read the memory remains of a previous instance. The issue is fixed in versions 36.0.7, 42.0.2, and 43.0.1.

Affected products

Bytecode Alliance Wasmtime >= 28.0.0, < 36.0.7; >= 37.0.0, < 42.0.2; 43.0.0

Identifiers

CVE-2026-34988
GHSA-6wgr-89rj-399p
RUSTSEC-2026-0088

Timeline

2026-04-09: disclosed
2026-04-09: advisory
2026-04-09: patched

References

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