CVE-2024-27308 is a high-severity (CVSS 7.5) Use After Free vulnerability in mio. A fix is available for mio — see the affected versions and patch details below.
Mio's tokens for named pipes may be delivered after deregistration
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-27308.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
mioReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Impact
When using named pipes on Windows, mio will under some circumstances return invalid tokens that correspond to named pipes that have already been deregistered from the mio registry. The impact of this vulnerability depends on how mio is used. For some applications, invalid tokens may be ignored or cause a warning or a crash. On the other hand, for applications that store pointers in the tokens, this vulnerability may result in a use-after-free.
For users of Tokio, this vulnerability is serious and can result in a use-after-free in Tokio.
The vulnerability is Windows-specific, and can only happen if you are using named pipes. Other IO resources are not affected.
Affected versions
This vulnerability has been fixed in mio v0.8.11.
All versions of mio between v0.7.2 and v0.8.10 are vulnerable.
Tokio is vulnerable when you are using a vulnerable version of mio AND you are using at least Tokio v1.30.0. Versions of Tokio prior to v1.30.0 will ignore invalid tokens, so they are not vulnerable.
Workarounds
Vulnerable libraries that use mio can work around this issue by detecting and ignoring invalid tokens.
Technical details
When an IO resource registered with mio has a readiness event, mio delivers that readiness event to the user using a user-specified token. Mio guarantees that when an IO resource is deregistered, then it will never return the token for that IO resource again. However, for named pipes on windows, mio may sometimes deliver the token for a named pipe even though the named pipe has been previously deregistered.
This vulnerability was originally reported in the Tokio issue tracker: tokio-rs/tokio#6369 This vulnerability was fixed in: tokio-rs/mio#1760 This vulnerability is also known as RUSTSEC-2024-0019.
Thank you to @rofoun and @radekvit for discovering and reporting this issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | mio | ≥ 0.7.2&&< 0.8.11 | 0.8.11cargo update -p mio --precise 0.8.11 |
Affected Products
miomio_projecttokiotokioDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mio, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mio to 0.8.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-27308 is resolved across your whole dependency graph.
Workarounds
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.
Frequently Asked Questions
Is CVE-2024-27308 in your dependencies?
Find it across crates.io, including transitive dependencies.