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CRITICAL severity

CVE-2019-25004 — flatbuffers

CRITICAL

CVE-2019-25004 is a critical-severity (CVSS 9.8) vulnerability in flatbuffers. 1 public exploit reference exists, so weaponization risk is real. A fix is available for flatbuffers — see the affected versions and patch details below.

Unsound casting in flatbuffers

Also known asRUSTSEC-2019-0028
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs46th percentile — riskier than 46% of all scored CVEsHighest risk
0.00%0.36%0.72%1.08%0.2%0.6%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2019-25004 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 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
🦀flatbuffers

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

The implementation of impl Follow for bool allows to reinterpret arbitrary bytes as a bool.

In Rust bool has stringent requirements for its in-memory representation. Use of this function allows to violate these requirements and invoke undefined behaviour in safe code.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.ioflatbuffers≥ 0.4.0&&< 0.6.10.6.1cargo update -p flatbuffers --precise 0.6.1

Affected Products

1 product · 1 configurations
Application
flatbuffersgoogle
≥ 0.4.0 && < 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 flatbuffers crate before 0.6.1 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 flatbuffers, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update flatbuffers to 0.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-25004 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

The implementation of impl Follow for bool allows to reinterpret arbitrary bytes as a bool. In Rust bool has stringent requirements for its in-memory representation. Use of this function allows to violate these requirements and invoke undefined behaviour in safe code.
O3 Security · Impact-Aware SCA

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CVE-2019-25004: flatbuffers — Fixed in 0.6.1