MEDIUM

CVE-2021-31806

CVSS v3

6.5

MEDIUM

EPSS Score

95.3 %

exploit probability, as of 2026-10-19

CISA KEV

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

libecapAlmaLinux:8all versions · fixed in 1.0.1-2.module_el8.6.0+2741+01592ae8and 1 other package
squidAlmaLinux:8all versions · fixed in 7:4.15-3.module_el8.6.0+3010+383bc947.1

Vendor advisories

CVE-2021-31806 Red Hat Product Security30 products fixed · 8 known affected
squid: improper input validation in HTTP Range header
squid as a component of Red Hat Enterprise Linux 6 · squid.src as a component of Red Hat Enterprise Linux 6 · squid34 as a component of Red Hat Enterprise Linux 6
RHSA-2021:4292 Red Hat Product Security30 products fixed
Red Hat Security Advisory: squid:4 security, bug fix, and enhancement update

Full record on NVD

Description

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.

Technical details

Published: 2021-05-27

Frequently asked questions

What is CVE-2021-31806?

Is CVE-2021-31806 actively exploited?

Active exploitation of CVE-2021-31806 has not been confirmed. Its EPSS score was 95.3% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-31806?

CVE-2021-31806 has a CVSS v3 base score of 6.5 (MEDIUM severity).

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