An issue was discovered in Squid before 4.15 and 5.x before 5.0.6.
Priority HIGH 73CWE-116Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 1 fixed, 2 without a fix
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat.
Summary
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.
Why it matters now
EPSS 0.95333 99th percentileScored 2026-11-07
Fix Partial Red Hat: 1 advisoryRed Hat: 1 fixed, 2 without a fix
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | — | all versions | — | No fix listed | CNA |
- — Vendor— Affected all versions Fixed in — No fix listed CNA
CPE configurations NVD · 6
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:* | before 4.15; 5.0 to before 5.0.6 | Vulnerable | squid-cache |
| cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* | 9.0 | Vulnerable | Debian |
| cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* | 10.0 | Vulnerable | Debian |
| cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:* | 33 | Vulnerable | Fedoraproject |
| cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* | 34 | Vulnerable | Fedoraproject |
| cpe:2.3:a:netapp:cloud_manager:-:*:*:*:*:*:*:* | not specified by NVD | Vulnerable | NetApp |
- cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:* Versions before 4.15; 5.0 to before 5.0.6 Vulnerable ·squid-cache
- cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* Versions 9.0 Vulnerable ·Debian
- cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* Versions 10.0 Vulnerable ·Debian
- cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:* Versions 33 Vulnerable ·Fedoraproject
- cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* Versions 34 Vulnerable ·Fedoraproject
- cpe:2.3:a:netapp:cloud_manager:-:*:*:*:*:*:*:* Versions not specified by NVD Vulnerable ·NetApp
Remediation
Red Hat 1 advisory
- RHSA-2021:4292 Released 2021-11-09 · Red Hat rating Moderatesquid:4 security, bug fix, and enhancement update
- Red Hat Enterprise Linux AppStream (v. 8) libecap-1.0.1-2.module+el8.1.0+4044+36416a77.aarch64::squid:4, libecap-1.0.1-2.module+el8.1.0+4044+36416a77.ppc64le::squid:4, libecap-1.0.1-2.module+el8.1.0+4044+36416a77.s390x::squid:4 +11
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux AppStream (v. 8) | Fixed | RHSA-2021:4292 |
Not affected: 1 product
- Red Hat Enterprise Linux 9
Timeline
- 2026-10-02 Threatist record created from CVE-2021-31806
- 2026-10-03 Alias added: GHSA-3v8m-hgx9-fgh9
References
Patch 2
Advisory 7
- DSA-4924
- FEDORA-2021-c0bec55ec7
- FEDORA-2021-24af72ff2c
- [debian-lts-announce] 20210614 [SECURITY] [DLA 2685-1] squid3 security update
- https://security.netapp.com/advisory/ntap-20210716-0007/
- [oss-security] 20231011 Squid Caching Proxy Security Audit: 55 Vulnerabilities, 35 0days.
- 20231016 Squid Caching Proxy Security Audit: 55 Vulnerabilities, 35 0days.
Sources
- CVE-2021-31806 · CVE Program
- CVE-2021-31806 · NVD
- FIRST EPSS
- GHSA-3v8m-hgx9-fgh9 · GitHub Advisory Database · CC BY 4.0
- CVE-2021-31806 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences