CVE-2021-31806

What it is

An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to a memory-management bug, it is vulnerable to a Denial of Service attack (against all clients using the proxy) via HTTP Range request processing.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of service disruption.

Exploit odds

95.3% chance of exploitation in the next 30 days (EPSS). Higher than most.

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-04-26 00:00 UTC ReservedThe CVE id was reserved by its CNA
2. 2021-05-27 13:15 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-06-17 03:52 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 95.3% in the next 30 days (EPSS).
• Severity: 6.5 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-05-27 13:15 UTC

Last modified

2026-06-17 03:52 UTC

Exploit probability

95.3% · EPSS, next 30 days

Weakness

CWE-116

Record status

Modified

Affected

• squid-cache Squid < 4.15
• squid-cache Squid < 5.0.6
• Debian Linux 9.0
• Debian Linux 10.0
• Fedoraproject Fedora 33
• Fedoraproject Fedora 34
• Netapp Cloud Manager

Attack profile CVSS 3.1 · 6.5

Attack vector

Network

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-31806.md and follow it. Check whether this project is affected by CVE-2021-31806. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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