MEDIUM
CVE-2021-31808
CWE-190Published: May 27, 2021· Updated: Jun 17, 2026
6.5
CVSS v3.1
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.
Technical Analysis
CVE-2021-31808 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
A successful exploit results in availability disruption (denial of service), with a CVSS base score of 6.5.
CVSS v3.1 Vector Breakdown
Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Affected Vendors & Products
Debian1 product(s)
debian linux
Fedora1 product(s)
fedora
netapp1 product(s)
cloud manager
squid-cache1 product(s)
squid
Source: NVD CPE · 6 total CPE entries
Exploit & PoC Resources
NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.
Official Patches & Advisories
All References (18)
→
http://seclists.org/fulldisclosure/2023/Oct/14Mailing List · Third Party Advisory
→
http://www.openwall.com/lists/oss-security/2023/10/11/3Mailing List · Third Party Advisory
→
http://www.squid-cache.org/Versions/v4/changesets/squid-4-e7cf864f938f24eea8af0692c04d16790983c823.patchExploit · Patch · Vendor Advisory
→
https://github.com/squid-cache/squid/security/advisories/GHSA-pxwq-f3qr-w2xfPatch · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2021/06/msg00014.htmlMailing List · Third Party Advisory
→
https://security.netapp.com/advisory/ntap-20210716-0007/Third Party Advisory
→
https://www.debian.org/security/2021/dsa-4924Third Party Advisory
→
http://seclists.org/fulldisclosure/2023/Oct/14Mailing List · Third Party Advisory
→
http://www.openwall.com/lists/oss-security/2023/10/11/3Mailing List · Third Party Advisory
→
http://www.squid-cache.org/Versions/v4/changesets/squid-4-e7cf864f938f24eea8af0692c04d16790983c823.patchExploit · Patch · Vendor Advisory
→
https://github.com/squid-cache/squid/security/advisories/GHSA-pxwq-f3qr-w2xfPatch · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2021/06/msg00014.htmlMailing List · Third Party Advisory
Quick Facts
CVE IDCVE-2021-31808
CVSS Score6.5 / 10
SeverityMEDIUM
WeaknessCWE-190
CISA KEVNo
Affected4 vendor(s)
PublishedMay 27, 2021
Related CVEs (CWE-190)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-31808 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.