CVE-2016-4556
No exploitation reported by the sources we read.
- Published2016-05-10
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
Description
Double free vulnerability in Esi.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows remote servers to cause a denial of service (crash) via a crafted Edge Side Includes (ESI) response.
Timeline
dates in UTC- 2016-05-1019:59CVE publishedNVD
- 2026-10-2319:23EPSS crossed 10 %FIRST EPSS
Observed activity
isMalicious corpus · updated 2026-10-23 21:37 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2016-4556?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2016-4556?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 3.0 | = 3.0 | no fix published | NVD |
| 3.1 | = 3.1 | no fix published | NVD |
| 3.1 | = 3.1.0.1 | no fix published | NVD |
| 3.1 | = 3.1.0.2 | no fix published | NVD |
| 3.1 | = 3.1.0.3 | no fix published | NVD |
| 3.1 | = 3.1.0.4 | no fix published | NVD |
| 3.1 | = 3.1.0.5 | no fix published | NVD |
| 3.1 | = 3.1.0.6 | no fix published | NVD |
| 3.1 | = 3.1.0.7 | no fix published | NVD |
| 3.1 | = 3.1.0.8 | no fix published | NVD |
| 3.1 | = 3.1.0.9 | no fix published | NVD |
| 3.1 | = 3.1.0.10 | no fix published | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 12.4 | = 12.04 | no fix published | NVD |
| 14.4 | = 14.04 | no fix published | NVD |
| 15.10 | = 15.10 | no fix published | NVD |
| 16.4 | = 16.04 | no fix published | NVD |
| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 6.x | = 6 | no fix published | NVD |
| 7.x | = 7 | no fix published | NVD |
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Fix
Advisories and patches
- www.openwall.comRelease Notes
- www.squid-cache.orgVendor Advisory
- www.squid-cache.orgPatch
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
- NVDCVSS 3.07.5read 2026-10-23
- NVDCVSS 2.05read 2026-10-23
- FIRST EPSSEPSS score23.1 %read 2026-10-23
Technical details
- CVSS v3 Vector
- CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Published
- 2016-05-10
- Last Modified
- 2026-06-17
- NVD status
- Modified
Frequently asked questions
What is CVE-2016-4556?
Is CVE-2016-4556 actively exploited?
What is the CVSS score for CVE-2016-4556?
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