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Fencer Intel
high 7.8

CVE-2021-3999 json

A flaw was found in glibc.

published 4y ago modified 26d ago also EUVD-2021-27189

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.8%
EPSS 0.8% chance of exploitation in 30 days, percentile 57%
public exploits
0
none known

Summary

A flaw was found in glibc. An off-by-one buffer overflow and underflow in getcwd() may lead to memory corruption when the size of the buffer is exactly 1. A local attacker who can control the input buffer and size passed to getcwd() in a setuid program could use this flaw to potentially execute arbitrary code and escalate their privileges on the system.

Patch / fix

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • glibc Debian 14, Debian 13, Debian 12 2.33-4

debian advisories DEBIAN-CVE-2021-3999

  • glibc Ubuntu 18.04 LTS 2.27-3ubuntu1.5
  • glibc Ubuntu 20.04 LTS 2.31-0ubuntu9.7
  • glibc Ubuntu Pro 16.04 LTS 2.23-0ubuntu11.3+esm1
  • eglibc Ubuntu Pro 14.04 LTS 2.19-0ubuntu6.15+esm3

ubuntu advisories UBUNTU-CVE-2021-3999

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • glibc RHEL 8 2.28-164.el8_5.3
  • nscd RHEL 8 2.28-164.el8_5.3
  • libnsl RHEL 8 2.28-164.el8_5.3
  • nss_db RHEL 8 2.28-164.el8_5.3
  • nss_hesiod RHEL 8 2.28-164.el8_5.3
  • glibc-utils RHEL 8 2.28-164.el8_5.3
  • glibc-common RHEL 8 2.28-164.el8_5.3
  • glibc-benchtests RHEL 8 2.28-164.el8_5.3

red hat advisories RHSA-2022:0896

  • glibc SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +4 more 2.22-119.1
  • glibc SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 2.11.3-17.110.40.1
  • glibc SLES for SAP 15 SP2, SLES for SAP 15 SP1, SLES for SAP 15 +18 more 2.26-13.65.1
  • glibc SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES 12 SP5 +4 more 2.22-114.19.1
  • glibc SLE Module for Development Tools 15 SP3, SLE Module for Basesystem 15 SP3, SLE Micro 5.1 2.31-150300.9.12.1

suse advisories SUSE-SU-2022:0909-1SUSE-SU-2022:14923-1SUSE-SU-2022:0832-1SUSE-SU-2022:0441-1SUSE-SU-2022:0330-1

  • glibc openSUSE Tumbleweed 2.35-1.1
  • glibc openSUSE Leap 15.3 2.31-150300.9.12.1

opensuse advisories openSUSE-SU-2024:11850-1openSUSE-SU-2022:0330-1

  • nss_hesiod AlmaLinux 8 2.28-164.el8_5.3
  • glibc-utils AlmaLinux 8 2.28-164.el8_5.3
  • glibc-benchtests AlmaLinux 8 2.28-164.el8_5.3
  • compat-libpthread-nonshared AlmaLinux 8 2.28-164.el8_5.3

almalinux advisories ALSA-2022:0896

  • glibc Rocky Linux 8 2.28-164.el8_5.3

rocky linux advisories RLSA-2022:0896

  • glibc Arch Linux 2.34-1

arch linux advisories AVG-1621

Is CVE-2021-3999 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

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-2021-3999 updated cvss 7.4

glibc: Off-by-one buffer overflow/underflow in getcwd()

  • Red Hat Enterprise Linux 6 nscd, glibc, glibc-utils, compat-glibc, glibc-common Red Hat Enterprise Linux 7 nscd, glibc, glibc-utils, compat-glibc, glibc-common
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat CodeReady Linux Builder (v. 8) nss_hesiod 2.28-164.el8_5.3, glibc-benchtests 2.28-164.el8_5.3, glibc-debuginfo-common 2.28-164.el8_5.3 Red Hat Enterprise Linux AppStream (v. 8) glibc-utils 2.28-164.el8_5.3, glibc-debuginfo-common 2.28-164.el8_5.3, compat-libpthread-nonshared 2.28-164.el8_5.3 Red Hat Enterprise Linux BaseOS (v. 8) nscd 2.28-164.el8_5.3, glibc 2.28-164.el8_5.3, libnsl 2.28-164.el8_5.3, nss_db 2.28-164.el8_5.3, glibc-common 2.28-164.el8_5.3, glibc-all-langpacks 2.28-164.el8_5.3, +3 more
    fixed: vendor fix RHSA-2022:0896
  • Red Hat Enterprise Linux 9 nscd, glibc, libnsl, nss_db, nss_hesiod, glibc-utils, +6 more
    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-23-348-10 updated cvss 7.8

Siemens SIMATIC S7-1500

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.0, < 3.1.5
    affected: fixed in V3.1.5, mitigation support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

cisa ICSA-23-166-10 updated cvss 7.8

Siemens SIMATIC S7-1500 TM MFP BIOS

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
11mo ago

Exploit prediction

0.81% chance of exploitation in the next 30 days, higher than 57% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • openwall.com https://www.openwall.com/lists/oss-security/2022/01/24/4 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

  • n/a glibc
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

Classification

Weakness

References

Sources

Fencer Intel 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.