CVE-2021-27645 Use after free in n/a

What is CVE-2021-27645?

CVE-2021-27645 is a low-severity use after free vulnerability in Debian Debian Linux, published on 24 Feb 2021. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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.

Weakness: CWE-415

Which versions are affected by CVE-2021-27645?

It affects 3 products.

Products include Debian Debian Linux, Fedoraproject Fedora, Gnu Glibc.

How do I fix CVE-2021-27645?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2021-27645 being exploited?

There is no known exploitation of CVE-2021-27645 in the wild and no public exploit code.

Other vulnerabilities in Debian Debian Linux

• CVE-2015-3306 ProFTPD Improper Access Control Exploited Critical 10.0
• CVE-2025-49113 RoundCube Webmail Deserialization of Untrusted Data Exploited Critical 9.9
• CVE-2026-24061 GNU InetUtils Argument Injection Exploited Critical 9.8
• CVE-2025-39682 Linux Kernel Improper Check for Unusual or Exceptional Conditions Exploited Critical 9.8
• CVE-2024-9680 Mozilla Firefox Use-After-Free Exploited Critical 9.8

All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2021-27645, GHSA-2hpw-5cjm-953f, MGASA-2021-0138, UBUNTU-CVE-2021-27645.