GHSA-q8hx-mm92-4wvg CVE-2024-47763 PYSEC-2024-312 RUSTSEC-2024-0440
wasmtime has a runtime crash when combining tail calls with trapping imports
- Severity
- 0.0 / 10
- Medium · CVSS 4.0
- Exploit chance (EPSS)
- 0.24%
- Chance of exploitation in the next 30 days. Higher than 15.73% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Fix
21.0.2- Upgrade wasmtime to this version or later
Description
Impact
Wasmtime's implementation of WebAssembly tail calls combined with stack traces can result in a runtime crash in certain WebAssembly modules. The runtime crash may be undefined behavior if Wasmtime was compiled with Rust 1.80 or prior. The runtime crash is a deterministic process abort when Wasmtime is compiled with Rust 1.81 and later.
WebAssembly tail calls are a proposal which relatively recently reached stage 4 in the standardization process. Wasmtime first enabled support for tail calls by default in Wasmtime 21.0.0, although that release contained a bug where it was only on-by-default for some configurations. In Wasmtime 22.0.0 tail calls were enabled by default for all configurations.
The specific crash happens when an exported function in a WebAssembly module (or component) performs a return_call (or return_call_indirect or return_call_ref) to an imported host function which captures a stack trace (for example, the host function raises a trap). In this situation, the stack-walking code previously assumed there was always at least one WebAssembly frame on the stack but with tail calls that is no longer true. With the tail-call proposal it's possible to have an entry trampoline appear as if it directly called the exit trampoline. This situation triggers an internal assert in the stack-walking code which raises a Rust panic!().
When Wasmtime is compiled with Rust versions 1.80 and prior this means that an extern "C" function in Rust is raising a panic!(). This is technically undefined behavior and typically manifests as a process abort when the unwinder fails to unwind Cranelift-generated frames. When Wasmtime is compiled with Rust versions 1.81 and later this panic becomes a deterministic process abort.
Overall the impact of this issue is that this is a denial-of-service vector where a malicious WebAssembly module or component can cause the host to crash. There is no other impact at this time other than availability of a service as the result of the crash is always a crash and no more.
This issue was discovered by routine fuzzing performed by the Wasmtime project via Google's OSS-Fuzz infrastructure. We have no evidence that it has ever been exploited by an attacker in the wild.
Patches
All versions of Wasmtime which have tail calls enabled by default have been patched:
- 21.0.x - patched in 21.0.2
- 22.0.x - patched in 22.0.1
- 23.0.x - patched in 23.0.3
- 24.0.x - patched in 24.0.1
- 25.0.x - patched in 25.0.2
Wasmtime versions from 12.0.x (the first release with experimental tail call support) to 20.0.x (the last release with tail-calls off-by-default) have support for tail calls but the support is disabled by default. These versions are not affected in their default configurations, but users who explicitly enabled tail call support will need to either disable tail call support or upgrade to a patched version of Wasmtime.
Workarounds
The main workaround for this issue is to disable tail support for tail calls in Wasmtime, for example with Config::wasm_tail_call(false). Users are otherwise encouraged to upgrade to patched versions.
References
Affected versions
PyPI
| Package | Vulnerable | Fixed in |
|---|---|---|
| wasmtime-bin | <= 21.0.0<= 21.0.1<= 22.0.0<= 23.0.0<= 23.0.1<= 23.0.2<= 24.0.0<= 25.0.0<= 25.0.1 |
No fix yet |
crates.io
| Package | Vulnerable | Fixed in |
|---|---|---|
| wasmtime | >= 12.0.0, < 21.0.2 |
21.0.2 |
| wasmtime | >= 22.0.0, < 22.0.1 |
22.0.1 |
| wasmtime | >= 23.0.0, < 23.0.3 |
23.0.3 |
| wasmtime | >= 24.0.0, < 24.0.1 |
24.0.1 |
| wasmtime | >= 25.0.0, < 25.0.2 |
25.0.2 |
| wasmtime | >= 21.0.0, < 21.0.2>= 22.0.0, < 22.0.1>= 23.0.0, < 23.0.3>= 24.0.0, < 24.0.1>= 25.0.0, < 25.0.2 |
21.0.222.0.123.0.324.0.125.0.2 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
wasmtime crates.io → 21.0.2
- cargo
cargo update -p wasmtime --precise 21.0.2
Severity breakdown
CVSS 4.0 0.0
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- Attack vector
- Local
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- Low
- User interaction
- None
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- None
- Availability (vulnerable system)
- High
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
CVSS 3.1 5.5
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Weakness
CWE-617: Reachable Assertion
The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.
How to prevent it
- Implementation: Make sensitive open/close operation non reachable by directly user-controlled data (e.g. open/close resources)
- Implementation: Perform input validation on user data.
CWE-670: Always-Incorrect Control Flow Implementation
The code contains a control flow path that does not reflect the algorithm that the path is intended to implement, leading to incorrect behavior any time this path is navigated.
References
Advisories
Packages
Other links
- github.com/bytecodealliance/wasmtime/security/advisories/GHSA-q8hx-mm92-4wvg
- github.com/bytecodealliance/wasmtime/pull/6774
- github.com/bytecodealliance/wasmtime/pull/8540
- github.com/bytecodealliance/wasmtime/pull/8682
- github.com/bytecodealliance/wasmtime/commit/0ebe54d05f0e1f6c64b7c8bb48c9e9f6c95…
- docs.rs/wasmtime/latest/wasmtime/struct.Config.html
- github.com/WebAssembly/proposals
- github.com/pypa/advisory-database/tree/main/vulns/wasmtime-bin/PYSEC-2024-312.yaml
- github.com/webassembly/tail-call
- rustsec.org/advisories/RUSTSEC-2024-0440.html
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| RUSTSEC-2026-0424 Unchecked memory usage in transferring borrowed resources between components | Not rated yet | Also affects wasmtime |
| RUSTSEC-2026-0423 Cross-engine type confusion with host-created struct-types-with-supertypes | Not rated yet | Also affects wasmtime |
| RUSTSEC-2026-0422 Typed functions with `i31` or `nullref` arguments may panic due to insufficient type-check | Low | Also affects wasmtime |
| RUSTSEC-2026-0379 Wasmtime: Cranelift backend on aarch64 can jump to incorrect target on large Wasm `br_table` instruction | Critical | Also affects wasmtime |
| GHSA-9pvw-hwfg-92h5 Wasmtime: Panic lowering a host-created component model stream into a guest that expects a different payload type | Medium | Also affects wasmtime |
| GHSA-897f-g5gm-fmxm Wasmtime: Bit-packing in Cranelift compiler causes silent overflow and miscompilation | Critical | Also affects wasmtime |
| RUSTSEC-2026-0364 Exception tags can cause host data structures to be unaligned | Not rated yet | Also affects wasmtime |
| RUSTSEC-2026-0363 Component-model handle tables are capped only per instance and charged to no limit | Medium | Also affects wasmtime |
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