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Fencer Vulns
low 2.5

CVE-2021-27645 json

The nameserver caching daemon (nscd) in the GNU C Library (aka glibc or libc6) 2.29 through 2.33, when processing a request for netgroup lo…

published 2021-02-24 5 y ago modified 2026-10-14 26 d ago also EUVD-2021-14391

cvss
2.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 32%
public exploits
0
none known

Summary

The nameserver caching daemon (nscd) in the GNU C Library (aka glibc or libc6) 2.29 through 2.33, when processing a request for netgroup lookup, may crash due to a double-free, potentially resulting in degraded service or Denial of Service on the local system. This is related to netgroupcache.c.

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 2.31-10

debian advisories DEBIAN-CVE-2021-27645

  • glibc Ubuntu 20.04 LTS 2.31-0ubuntu9.7

ubuntu advisories UBUNTU-CVE-2021-27645

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
  • nscd RHEL 8 2.28-164.el8
  • libnsl RHEL 8 2.28-164.el8
  • nss_db RHEL 8 2.28-164.el8
  • nss_hesiod RHEL 8 2.28-164.el8
  • glibc-utils RHEL 8 2.28-164.el8
  • glibc-common RHEL 8 2.28-164.el8
  • glibc-benchtests RHEL 8 2.28-164.el8

red hat advisories RHSA-2021:4358

  • glibc openSUSE Tumbleweed 2.34-1.2

opensuse advisories openSUSE-SU-2024:10792-1

  • nss_hesiod AlmaLinux 8 2.28-164.el8
  • glibc-utils AlmaLinux 8 2.28-164.el8
  • glibc-benchtests AlmaLinux 8 2.28-164.el8
  • compat-libpthread-nonshared AlmaLinux 8 2.28-164.el8

almalinux advisories ALSA-2021:4358

  • glibc Rocky Linux 8 2.28-164.el8

rocky linux advisories RLSA-2021:4358

  • glibc Arch Linux 2.34-1

arch linux advisories AVG-1621

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-2021-27645 updated cvss 2.5

glibc: Use-after-free in addgetnetgrentX function in netgroupcache.c

  • Red Hat CodeReady Linux Builder (v. 8) nscd 2.28-164.el8, glibc 2.28-164.el8, libnsl 2.28-164.el8, nss_db 2.28-164.el8, nss_hesiod 2.28-164.el8, glibc-utils 2.28-164.el8, +7 more Red Hat Enterprise Linux AppStream (v. 8) nscd 2.28-164.el8, glibc 2.28-164.el8, libnsl 2.28-164.el8, nss_db 2.28-164.el8, nss_hesiod 2.28-164.el8, glibc-utils 2.28-164.el8, +7 more Red Hat Enterprise Linux BaseOS (v. 8) nscd 2.28-164.el8, glibc 2.28-164.el8, libnsl 2.28-164.el8, nss_db 2.28-164.el8, nss_hesiod 2.28-164.el8, glibc-utils 2.28-164.el8, +7 more
    fixed: vendor fix RHSA-2021:4358
  • 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 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 2.5

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 2.5

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
partial
Assessed
17 mo ago

Exploit prediction

0.39% chance of exploitation in the next 30 days, higher than 32% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 2.5 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
NVD 3.1 2.5 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
CNA 3.1 2.5 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
NVD 2.0 1.9 AV:L/AC:M/Au:N/C:N/I:N/A:P

Affected products

  • 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 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.