CVE-2021-25900: Buffer overflow in SmallVec::insert_many

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.7% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-01-26 · updated 2026-06-17
Weakness: CWE-787

Description

An issue was discovered in the smallvec crate before 0.6.14 and 1.x before 1.6.1 for Rust. There is a heap-based buffer overflow in SmallVec::insert_many.

Affected products

servo Smallvec: from 0.6.3 before 0.6.14; from 1.0.0 before 1.6.1 — fixed in 0.6.14, 1.6.1
Crates.Io Smallvec: from 0.6.3 before 0.6.14; from 1.0.0 before 1.6.1 — fixed in 0.6.14, 1.6.1

How to fix

Upgrade to a fixed version: servo Smallvec 0.6.14, 1.6.1; Crates.Io Smallvec 0.6.14, 1.6.1. Check the vendor advisory for mitigations.

References

https://rustsec.org/advisories/RUSTSEC-2021-0003.html
https://rustsec.org/advisories/RUSTSEC-2021-0003.html

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