{"id":"CVE-2018-1000027","url":"https://www.cyber-defence.io/tools/cve/CVE-2018-1000027","generatedAt":"2026-10-29T01:55:20.826Z","title":"The Squid Software Foundation Squid HTTP Caching Proxy version prior to version 4.0.23 contains a NULL Pointer Dereference vulnerability in HTTP Response X-Forwarded-For header processing that can result in Denial of Service to all clients of the proxy.","description":"The Squid Software Foundation Squid HTTP Caching Proxy version prior to version 4.0.23 contains a NULL Pointer Dereference vulnerability in HTTP Response X-Forwarded-For header processing that can result in Denial of Service to all clients of the proxy. This attack appear to be exploitable via Remote HTTP server responding with an X-Forwarded-For header to certain types of HTTP request. This vulnerability appears to have been fixed in 4.0.23 and later.","published":"2018-02-09T23:29:01.000Z","lastModified":"2026-06-17T01:32:14.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.0","score":7.5,"severity":"HIGH","vector":"CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-476"],"affected":["squid-cache/squid","debian/debian linux","canonical/ubuntu linux"],"epss":{"score":0.12912,"percentile":0.96287,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"urgent","text":"EPSS puts the probability of exploitation in the next 30 days at 12.9%, higher than 96% of all known CVEs. Patch or mitigate before the next change window."},"changes":[],"references":[{"url":"http://www.squid-cache.org/Advisories/SQUID-2018_2.txt","tags":["Patch","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"http://www.squid-cache.org/Versions/v3/3.5/changesets/SQUID-2018_2.patch","tags":["Patch","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"http://www.squid-cache.org/Versions/v4/changesets/SQUID-2018_2.patch","tags":["Patch","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://github.com/squid-cache/squid/pull/129/files","tags":["Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://lists.debian.org/debian-lts-announce/2018/02/msg00001.html","tags":["Mailing List","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://lists.debian.org/debian-lts-announce/2018/02/msg00002.html","tags":["Mailing List","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://usn.ubuntu.com/3557-1/","tags":["Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://usn.ubuntu.com/4059-2/","source":"cve@mitre.org"},{"url":"https://www.debian.org/security/2018/dsa-4122","tags":["Third Party Advisory"],"source":"cve@mitre.org"},{"url":"http://www.squid-cache.org/Advisories/SQUID-2018_2.txt","tags":["Patch","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://www.squid-cache.org/Versions/v3/3.5/changesets/SQUID-2018_2.patch","tags":["Patch","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://www.squid-cache.org/Versions/v4/changesets/SQUID-2018_2.patch","tags":["Patch","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://github.com/squid-cache/squid/pull/129/files","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2018/02/msg00001.html","tags":["Mailing List","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2018/02/msg00002.html","tags":["Mailing List","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://usn.ubuntu.com/3557-1/","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://usn.ubuntu.com/4059-2/","source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.debian.org/security/2018/dsa-4122","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2018-1000027","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}