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Not in CISA KEV
MEDIUM severity

CVE-2020-35907 — futures-task

MEDIUM

CVE-2020-35907 is a medium-severity (CVSS 5.5) NULL Pointer Dereference 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::noop_waker_ref can segfault due to dereferencing a NULL pointer

Also known asGHSA-p9m5-3hj7-cp5rRUSTSEC-2020-0061
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Nov 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs35th percentile — riskier than 35% of all scored CVEsHighest risk
0.00%0.30%0.60%0.91%0.1%0.4%May 26Sep 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 used a UnsafeCell in thread-local storage to return a noop waker reference, assuming that the reference would never be returned from another thread.

This resulted in a segmentation fault crash if Waker::wake_by_ref() was called on a waker returned from another thread due to it attempting to dereference a pointer that wasn't accessible from the main thread.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.iofutures-taskall versions0.3.5cargo update -p futures-task --precise 0.3.5

Affected Products

1 product · 1 configurations
Application
futures-taskrust-lang
< 0.3.5
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 0.3.5 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 0.3.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-35907 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

Affected versions of the crate used a UnsafeCell in thread-local storage to return a noop waker reference, assuming that the reference would never be returned from another thread. This resulted in a segmentation fault crash if Waker::wake_by_ref() was called on a waker returned from another thread due to it attempting to dereference a pointer that wasn't accessible from the main thread.
O3 Security · Impact-Aware SCA

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CVE-2020-35907: futures-task — Fixed in 0.3.5