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CRITICAL severity

CVE-2019-15551 — smallvec

CRITICALFix: servo/rust-smallvec@c20cfa8

CVE-2019-15551 is a critical-severity (CVSS 9.8) CWE-415 vulnerability in smallvec. A fix is available for smallvec — see the affected versions and patch details below.

Double free in smallvec

Also known asGHSA-mm7v-vpv8-xfc3RUSTSEC-2019-0009
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs79th percentile — riskier than 79% of all scored CVEsHighest risk
0.00%0.79%1.57%2.36%0.4%1.9%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2019-15551 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,386 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
🦀smallvec

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

Attempting to call grow on a spilled SmallVec with a value equal to the current capacity causes it to free the existing data. This performs a double free immediately and may lead to use-after-free on subsequent accesses to the SmallVec contents. An attacker that controls the value passed to grow may exploit this flaw to obtain memory contents or gain remote code execution.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.iosmallvec≥ 0.6.5&&< 0.6.100.6.10cargo update -p smallvec --precise 0.6.10

Affected Products

1 product · 1 configurations
Application
smallvecservo
≥ 0.6.5 && < 0.6.10
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update smallvec to 0.6.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-15551 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

Attempting to call grow on a spilled SmallVec with a value equal to the current capacity causes it to free the existing data. This performs a double free immediately and may lead to use-after-free on subsequent accesses to the SmallVec contents. An attacker that controls the value passed to grow may exploit this flaw to obtain memory contents or gain remote code execution.
O3 Security · Impact-Aware SCA

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CVE-2019-15551: smallvec RCE — Fixed in 0.6.10