CVE-2016-4553

HIGHNVD 8.69.0▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.0 because EPSS predicts 80% probability of exploitation within the next 30 days (top 0.4% of all CVEs). NVD baseline CVSS 8.6 retained for reference. Confidence: see factors.

Triggered by: EPSS exploit prediction ≥85%
Sources: epss, ghsa, nvd
Elevated
8.6
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 80%
CISA-KEV: Not listedEPSS: 80%CVSS: 8.6Exploit: NoneExposed: 0

A fix is available — apply it.

client_side.cc in Squid before 3.5.18 and 4.x before 4.0.10 does not properly ignore the Host header when absolute-URI is provided, which allows remote attackers to conduct cache-poisoning attacks via an HTTP request.

CVSS v3
8.6
EG Score
9.0(high)
EG Risk
77(Track)
EG Risk 77/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity90% × 45%
Exploitation80% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
99.6%
KEV
Not listed

Published

May 10, 2016

Last Modified

May 6, 2026

References (26)

Patch Availability(3)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntusquidclient (3.5.12-1ubuntu7.2) @ xenial2026-05-22ubuntu
redhatsquid34-7:3.4.14-9.el6_8.32016-05-31redhat
redhatsquid-7:3.3.8-26.el7_2.32016-05-31redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

All Vendor Advisories

(3)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 6× in last 7d / 19× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-23 01:23 UTCEG score recompute▲ 0.40
  2. 2026-07-22 22:02 UTCEG score recompute
  3. 2026-07-22 14:04 UTCEPSS rescore
  4. 2026-07-21 15:21 UTCEPSS rescore
  5. 2026-07-21 15:21 UTCEPSS rescore
  6. 2026-07-20 17:03 UTCEPSS rescore
  7. 2026-07-16 16:59 UTCEPSS rescore
  8. 2026-07-16 16:59 UTCEPSS rescore
  9. 2026-07-15 16:54 UTCEPSS rescore
  10. 2026-07-15 16:54 UTCEPSS rescore
  11. 2026-07-13 06:09 UTCEPSS rescore
  12. 2026-07-12 10:08 UTCOSV refresh
  13. 2026-07-11 08:23 UTCEPSS rescore
  14. 2026-07-06 16:24 UTCEPSS rescore
  15. 2026-07-06 16:24 UTCEPSS rescore
  16. 2026-07-01 15:02 UTCEPSS rescore
  17. 2026-06-28 04:53 UTCEPSS rescore
  18. 2026-06-25 13:47 UTCEPSS rescore
  19. 2026-06-25 13:47 UTCEPSS rescore
  20. 2026-06-24 14:02 UTCEPSS rescore
  21. 2026-06-24 14:02 UTCEPSS rescore
  22. 2026-06-23 21:30 UTCEPSS rescore
  23. 2026-06-23 15:30 UTCOSV refresh
  24. 2026-06-21 14:54 UTCEPSS rescore
  25. 2026-06-21 14:54 UTCEPSS rescore
Show 27 more
  1. 2026-06-17 17:50 UTCEPSS rescore
  2. 2026-06-17 17:50 UTCEPSS rescore
  3. 2026-06-15 17:45 UTCEPSS rescore
  4. 2026-06-14 23:14 UTCEPSS rescore
  5. 2026-06-12 23:09 UTCEPSS rescore
  6. 2026-06-12 23:09 UTCEPSS rescore
  7. 2026-06-10 22:15 UTCEPSS rescore
  8. 2026-06-10 13:18 UTCEPSS rescore
  9. 2026-06-08 14:14 UTCEPSS rescore
  10. 2026-06-06 19:59 UTCOSV refresh
  11. 2026-06-05 22:44 UTCEPSS rescore
  12. 2026-06-04 13:10 UTCEPSS rescore
  13. 2026-06-04 13:10 UTCEPSS rescore
  14. 2026-05-31 00:14 UTCEPSS rescore
  15. 2026-05-28 13:42 UTCEPSS rescore
  16. 2026-05-28 13:42 UTCEPSS rescore
  17. 2026-05-22 21:15 UTCEPSS rescore
  18. 2026-05-22 21:15 UTCEPSS rescore
  19. 2026-05-22 20:27 UTCEG score recompute
  20. 2026-05-22 20:27 UTCVendor advisory
  21. 2026-05-22 20:27 UTCGHSA enrichment
  22. 2026-05-21 22:40 UTCEPSS rescore
  23. 2026-05-20 22:37 UTCEPSS rescore
  24. 2026-05-20 22:37 UTCEPSS rescore
  25. 2026-05-20 22:37 UTCEPSS rescore
  26. 2026-05-18 21:30 UTCEPSS rescore
  27. 2026-05-18 21:30 UTCEPSS rescore

Frequently asked(5)

What is CVE-2016-4553?
CVE-2016-4553 is a high vulnerability published on May 10, 2016. client_side.cc in Squid before 3.5.18 and 4.x before 4.0.10 does not properly ignore the Host header when absolute-URI is provided, which allows remote attackers to conduct cache-poisoning attacks via an HTTP request.
When was CVE-2016-4553 disclosed?
CVE-2016-4553 was first published in the National Vulnerability Database on May 10, 2016, with the most recent update on May 6, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2016-4553 actively exploited?
CVE-2016-4553 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 99.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2016-4553?
CVE-2016-4553 has a CVSS v3 base score of 8.6 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.
How do I remediate CVE-2016-4553?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2016-4553, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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