CVE-2018-20721 Memory corruption in n/a

What is CVE-2018-20721?

CVE-2018-20721 is a critical memory corruption vulnerability in Debian Debian Linux, published on 16 Jan 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

URI_FUNC() in UriParse.c in uriparser before 0.9.1 has an out-of-bounds read (in uriParse*Ex* functions) for an incomplete URI with an IPv6 address containing an embedded IPv4 address, such as a "//[::44.1" address.

Weakness: CWE-125

Which versions are affected by CVE-2018-20721?

It affects 2 products.

Products include Debian Debian Linux, Uriparser Project Uriparser.

How do I fix CVE-2018-20721?

Upgrade to a fixed version.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2018-20721 being exploited?

There is no known exploitation of CVE-2018-20721 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-2018-20721, DLA-1682-1, DLA-2834-1, GHSA-vxxw-p73w-mwf4, UBUNTU-CVE-2018-20721.