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CVE-2021-27645VulnerabilityPublished Updated

CVE-2021-27645: n/a

Source CVE Database V5

0

Not known to be exploited · CVSS 2.5 Low.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score
2.5Low
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 32% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Feb 2021

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.

What to do

Affected software

ProductAffectedFixed in
Debiandebian/libc6pkg:deb/debian/libc6Other threatsAffected
  • >=2.29 <=2.33
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should ensure that all systems running glibc versions 2.29 through 2.33 are updated to versions where this vulnerability is patched. Since no direct patch links are provided, administrators should consult their Linux distribution vendors (e.g., Debian, Ubuntu, Red Hat, SUSE) for glibc security updates and apply them promptly. Additionally, if nscd is not required, consider disabling the service to reduce the attack surface. For systems that must run nscd, restrict local access to trusted users only and monitor for unusual crashes or service disruptions related to nscd. Implementing strict access controls and auditing local user activities can help detect attempts to exploit this vulnerability. Finally, ensure that system and application logs are collected and analyzed to identify potential exploitation attempts or anomalous behavior related to name service caching.

Description

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.

References

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