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Fencer Vulns
critical 9.8

CVE-2021-3420 json

A flaw was found in newlib in versions prior to 4.0.0.

published 2021-03-05 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-26748

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.1%
EPSS 2.1% chance of exploitation in 30 days, percentile 81%
public exploits
0
none known

Summary

A flaw was found in newlib in versions prior to 4.0.0. Improper overflow validation in the memory allocation functions mEMALIGn, pvALLOc, nano_memalign, nano_valloc, nano_pvalloc could case an integer overflow, leading to an allocation of a small buffer and then to a heap-based buffer overflow.

Patch / fix

  • newlib_project newlib 4.0.0
  • newlib Debian 12 3.3.0-1.3+deb12u1
  • newlib Debian 14, Debian 13 4.4.0.20231231-2
  • picolibc Debian 14, Debian 13, Debian 12 1.5-1

debian advisories DEBIAN-CVE-2021-3420

  • newlib openSUSE Tumbleweed 4.1.0-2.2

opensuse advisories openSUSE-SU-2024:11086-1

  • newlib Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 4.1.0-r0

alpine advisories ALPINE-CVE-2021-3420

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

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-2021-3420 updated cvss 7.5

newlib: improper validation in memory allocation functions could lead to heap-based buffer overflow

  • 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

cisa ICSA-21-119-04 updated cvss 7.3

Multiple RTOS (Update E)

  • multiple Amazon FreeRTOS 10.4.1 multiple Apache Nuttx OS 9.1.0 multiple ARM CMSIS-RTOS2 < 2.1.3 multiple ARM Mbed OS 6.3.0 multiple ARM mbed-ualloc 1.3.0 multiple BlackBerry QNX OS for Medical <= 1.1
    +22 more products
    multiple BlackBerry QNX OS for Safety <= 1.0.1 multiple BlackBerry QNX SDP <= 6.5.0 SP1 multiple Cesanta Software Mongoose OS 2.17.0 multiple eCosCentric eCosPro RTOS >= 2.0.1, <= 4.5.3 multiple Google Cloud IoT Device SDK 1.0.2 multiple Media Tek LinkIt SDK < 4.6.1 multiple Micrium OS <= 5.10.1 multiple Micrium uC/OS 1.38.xx, 1.39.00 multiple NXP MCUXpresso SDK < 2.8.2 multiple NXP MQX <= 5.1 multiple Redhat newlib < 4.0.0 multiple RIOT OS 2020.01.1 multiple Samsung Tizen RT RTOS < 3.0.GBB multiple TencentOS-tiny 3.1.0 multiple Texas Instruments CC32XX < 4.40.00.07 multiple Texas Instruments SimpleLink MSP432E4XX multiple Texas Instruments SimpleLink-CC13XX < 4.40.00 multiple Texas Instruments SimpleLink-CC26XX < 4.40.00 multiple Texas Instruments SimpleLink-CC32XX < 4.10.03 multiple Uclibc-NG < 1.0.36 multiple Windriver VxWorks < 7.0 multiple Zephyr Project RTOS < 2.5
    affected: mitigation “Hitachi Energy GMS600 - See public advisory.” search.abb.com

From CISA ICS and IT advisories (CSAF, https://github.com/cisagov/CSAF), a U.S. Government work; changed: reduced to products, statuses and remediations. CISA notification · csaf

Exploit prediction

2.10% chance of exploitation in the next 30 days, higher than 81% of all scored CVEs (FIRST EPSS, 2026-11-08).

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

Affected products

  • n/a newlib

Classification

Weakness
  • CWE-190 Integer Overflow or Wraparound

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.