CVE-2021-31808 Denial of service in n/a

What is CVE-2021-31808?

CVE-2021-31808 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 27 May 2021. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to an input-validation bug, it is vulnerable to a Denial of Service attack (against all clients using the proxy). A client sends an HTTP Range request to trigger this.

Weakness: CWE-190

Which versions are affected by CVE-2021-31808?

It affects 4 products.

Products include Debian Debian Linux, Fedoraproject Fedora, Netapp Cloud Manager, Squid-Cache Squid.

How do I fix CVE-2021-31808?

Upgrade to a fixed version.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2021-31808 being exploited?

There is no known exploitation of CVE-2021-31808 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 ALPINE-CVE-2021-31808, DEBIAN-CVE-2021-31808, GHSA-hx5h-cw5j-ghcr, UBUNTU-CVE-2021-31808.