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🦀 crates.io
Not in CISA KEV
HIGH severity

CVE-2020-35906 — futures-task

HIGHFix: rust-lang/futures-rs#2206

CVE-2020-35906 is a high-severity (CVSS 7.8) Use After Free vulnerability in futures-task. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for futures-task — see the affected versions and patch details below.

futures_task::waker may cause a use-after-free if used on a type that isn't 'static

Also known asGHSA-r93v-9p5q-vhpfRUSTSEC-2020-0060
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Nov 1, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs43th percentile — riskier than 43% of all scored CVEsHighest risk
0.00%0.33%0.67%1.00%0.1%0.5%May 26Aug 26Nov 26

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

1 pkg affected
🦀futures-task

Real-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

Affected versions of the crate did not properly implement a 'static lifetime bound on the waker function. This resulted in a use-after-free if Waker::wake() is called after original data had been dropped.

The flaw was corrected by adding 'static lifetime bound to the data waker takes.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.iofutures-task≥ 0.2.1&&< 0.3.60.3.6cargo update -p futures-task --precise 0.3.6

Affected Products

1 product · 1 configurations
Application
futures-taskrust-lang
≥ 0.2.1 && < 0.3.6
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

An issue was discovered in the futures-task crate before 0.3.6 for Rust.…

rustsec.orgNVDJan 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for futures-task, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update futures-task to 0.3.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-35906 is resolved across your whole dependency graph.

  3. 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

Affected versions of the crate did not properly implement a 'static lifetime bound on the waker function. This resulted in a use-after-free if Waker::wake() is called after original data had been dropped. The flaw was corrected by adding 'static lifetime bound to the data waker takes.
O3 Security · Impact-Aware SCA

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CVE-2020-35906: futures-task — Fixed in 0.3.6