CVE-2021-25900

Exp

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.

Published: 2021-01-26 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-25900 is rated High Exploit Risk (81/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 1.65%). 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +1.11% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-25900

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-25900

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.55% 1.65% +1.11%
2 2025-11-21 0.45% 0.55% +0.10%
3 2025-11-18 — 0.45% —

Full EPSS history (13 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-25900

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
7.5 2.0 HIGH
AV:N/AC:L/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 6.4 [email protected]

Weakness enumeration for CVE-2021-25900

GitHub Security Advisory for CVE-2021-25900

GHSA-43w2-9j62-hq99 · Severity: critical · Ecosystem: rust — Buffer overflow in SmallVec::insert_many

OS Trackers for CVE-2021-25900

vendor priority summary link
debian not yet assigned CVE-2021-25900 not yet assigned priority: Debian including 1 source packages (rust-smallvec), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-25900
suse high CVE-2021-25900 severity important: SUSE including 92 source package names (cargo, cargo1.53, …), 249 product×package rows across 57 product lines (Image SLES15-SP3-SAP-Azure-LI-BYOS-Production, Image SLES15-SP3-SAP-Azure-VLI-BYOS-Production, … (57 product lines)): Known Not Affected 168, Fixed 81. https://www.suse.com/security/cve/CVE-2021-25900/
ubuntu medium CVE-2021-25900 medium priority: Ubuntu including 1 source packages (rust-smallvec), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): ignored 8, needed 4, DNE 3, needs-triage 1. https://ubuntu.com/security/CVE-2021-25900

Affected software / configurations for CVE-2021-25900

Vendor Product Version Raw CPE
servo smallvec >= 0.6.3, < 0.6.14 cpe:2.3:a:servo:smallvec:*:*:*:*:*:rust:*:*
servo smallvec >= 1.0.0, < 1.6.1 cpe:2.3:a:servo:smallvec:*:*:*:*:*:rust:*:*

References for CVE-2021-25900

URL Tags
https://rustsec.org/advisories/RUSTSEC-2021-0003.html Exploit Patch Third Party Advisory
cvelogic Threat Intelligence