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CRITICAL severity

CVE-2020-35858 — prost

CRITICALFix: danburkert/prost@04091d3

CVE-2020-35858 is a critical-severity (CVSS 9.8) Out-of-bounds Write vulnerability in prost. 1 public exploit reference exists, so weaponization risk is real. A fix is available for prost — see the affected versions and patch details below.

Out of bounds write in prost

Also known asGHSA-gv73-9mwv-fwgqRUSTSEC-2020-0002
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
3.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs89th percentile — riskier than 89% of all scored CVEsHighest risk
1.98%2.62%3.26%3.90%2.5%3.4%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2020-35858 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🦀prost

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 this crate contained a bug in which decoding untrusted input could overflow the stack. On architectures with stack probes (like x86), this can be used for denial of service attacks, while on architectures without stack probes (like ARM) overflowing the stack is unsound and can result in potential memory corruption (or even RCE).

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.ioprostall versions0.6.1cargo update -p prost --precise 0.6.1

Affected Products

1 product · 1 configurations
Application
prostprost_project
< 0.6.1
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 prost crate before 0.6.1 for Rust. There …

rustsec.orgNVDJul 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 prost, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update prost to 0.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-35858 is resolved across your whole dependency graph.

  3. Workarounds

    Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Frequently Asked Questions

Affected versions of this crate contained a bug in which decoding untrusted input could overflow the stack. On architectures with stack probes (like x86), this can be used for denial of service attacks, while on architectures without stack probes (like ARM) overflowing the stack is unsound and can result in potential memory corruption (or even RCE).
O3 Security · Impact-Aware SCA

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CVE-2020-35858: prost RCE — Fixed in 0.6.1