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Fencer Vulns
critical 9.8

CVE-2021-25900 json

Buffer overflow in SmallVec::insert_many

published 2021-01-08 5 y ago modified 2026-07-17 3 mo ago also GHSA-43w2-9j62-hq99 , RUSTSEC-2021-0003 , EUVD-2022-2287

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.7%
EPSS 1.7% chance of exploitation in 30 days, percentile 77%
public exploits
0
none known

Summary

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.

Patch / fix

  • crates.io smallvec 0.6.14, 1.6.1
  • servo smallvec 0.6.14, 1.6.1
  • rust-smallvec Debian 14, Debian 13, Debian 12 1.4.2-2

debian advisories DEBIAN-CVE-2021-25900

  • librsvg SLE Module for Desktop Applications 15 SP2, SLE Module for Basesystem 15 SP2 2.46.5-3.3.1

suse advisories SUSE-SU-2021:1408-1

  • librsvg openSUSE Leap 15.2 2.46.5-lp152.2.3.1

opensuse advisories openSUSE-SU-2021:0634-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-25900 updated cvss 9.8

rust-smallvec: heap-based buffer overflow in SmallVec::insert_many

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.72% chance of exploitation in the next 30 days, higher than 77% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • rustsec.org https://rustsec.org/advisories/RUSTSEC-2021-0003.html referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P
OSV 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
GitHub 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
crates.io smallvec
>=0.6.3, <0.6.14
>=1.0.0, <1.6.1
0.6.14
1.6.1

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.