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Vulnerability record · CVE-2019-18676 · published 26 November 2019

CVE-2019-18676: Squid-cache squid out-of-bounds write vulnerability

Squid Cache · Squid

An issue was discovered in Squid 3.x and 4.x through 4.8. Due to incorrect input validation, there is a heap-based buffer overflow that can result in Denial of Service to all clients using the proxy. Severity is high due to this vulnerability occurring before normal security checks; any remote client that can reach the proxy port can trivially perform the attack via a crafted URI scheme.

7.5 CVSS 3.1 High EPSS 9.2% · top 4.8% CWE-787 · Out-of-bounds write
7.5CVSS 3.1 base score, v2 5.0
9.2%EPSS exploitation probability, 30 days
NoNot in CISA KEV
4Affected product versions listed by NVD
20References
17 Jun 2026Last modified by NVD

Description

An issue was discovered in Squid 3.x and 4.x through 4.8. Due to incorrect input validation, there is a heap-based buffer overflow that can result in Denial of Service to all clients using the proxy. Severity is high due to this vulnerability occurring before normal security checks; any remote client that can reach the proxy port can trivially perform the attack via a crafted URI scheme.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

4 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://www.squid-cache.org/Advisories/SQUID-2019_8.txt Third Party Advisory
http://www.squid-cache.org/Versions/v4/changesets/squid-4-fbbdf75efd7a5cc244b4886a9d42ea458c5a3a73.patch Patch
https://bugzilla.suse.com/show_bug.cgi?id=1156329 Issue TrackingThird Party Advisory
https://github.com/squid-cache/squid/pull/275 PatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MTM74TU2BSLT5B3H4F3UDW5
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UEMOYTMCCFWK5NOXSXEIH5D
https://usn.ubuntu.com/4213-1/ Third Party Advisory
https://usn.ubuntu.com/4446-1/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4682 Third Party Advisory
http://www.squid-cache.org/Advisories/SQUID-2019_8.txt Third Party Advisory
http://www.squid-cache.org/Versions/v4/changesets/squid-4-fbbdf75efd7a5cc244b4886a9d42ea458c5a3a73.patch Patch
https://bugzilla.suse.com/show_bug.cgi?id=1156329 Issue TrackingThird Party Advisory
https://github.com/squid-cache/squid/pull/275 PatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MTM74TU2BSLT5B3H4F3UDW5
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UEMOYTMCCFWK5NOXSXEIH5D
https://usn.ubuntu.com/4213-1/ Third Party Advisory
https://usn.ubuntu.com/4446-1/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4682 Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2019-18676), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.