CVE-2013-4123

MEDIUMCVSS v2 · 5.05.0—
EchelonGraph scoreLOW confidence

This CVE was only ever scored under CVSS v2.0. NVD CVSS v2.0 base 5.0 — v2 rates that MEDIUM (v2 bands: LOW 0.0–3.9 / MEDIUM 4.0–6.9 / HIGH 7.0–10.0; v2 has no CRITICAL band). Vector AV:N/AC:L/Au:N/C:N/I:N/A:P. CVSS v2 is an older, coarser metric than v3.1/v4.0 (no Scope, no User Interaction, no Attack Requirements), so it is not directly comparable to a v3 or v4 score. NVD has never re-scored this record under v3. EPSS predicts 80.5% exploitation probability in the next 30 days, which is reflected in EG Risk but does not lift the v2 base. Confidence: LOW.

Sources: epss, nvd_v2
Weaponized
5.0EG
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 80%
  • Public exploit code is available (Exploit-DB (verified), epss top5pct, epss high, public exploit)
CISA-KEV: Not listedEPSS PROB: 80%CVSS v2: 5.0Exploit: Exploit-DB (verified) · epss top5pct · epss high · public exploitExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

client_side_request.cc in Squid 3.2.x before 3.2.13 and 3.3.x before 3.3.8 allows remote attackers to cause a denial of service via a crafted port number in a HTTP Host header.

CVSS v2.0 (legacy)
5.0MEDIUMNVD never assigned a CVSS v3 rating to this CVE
EG Score
5.0(low)
EG Risk
59(Track)
EG Risk 59/100SSVC: 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
Severity50% × 45%
Exploitation80% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
80%
EPSS %ILE
100%
KEV
Not listed

Published

September 16, 2013

Last Modified

April 29, 2026

References (12)

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 4× in last 7d / 10× 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. 2026-08-21 23:44 UTCEPSS rescore
  2. 2026-08-20 22:50 UTCEPSS rescore
  3. 2026-08-19 16:59 UTCEPSS rescore
  4. 2026-08-16 02:09 UTCEPSS rescore
  5. 2026-08-15 01:25 UTCEPSS rescore
  6. 2026-08-12 13:45 UTCEPSS rescore
  7. 2026-08-06 13:42 UTCEPSS rescore
  8. 2026-08-02 02:22 UTCEPSS rescore
  9. 2026-07-26 13:48 UTCEG score recompute▲ 5.00
  10. 2026-07-25 14:12 UTCEPSS rescore
  11. 2026-07-23 01:10 UTCEG score recompute▼ 8.30
  12. 2026-07-23 00:13 UTCEG score recompute▲ 8.30
  13. 2026-07-22 21:52 UTCEG score recompute
  14. 2026-07-22 14:04 UTCEPSS rescore
  15. 2026-07-22 14:04 UTCEPSS rescore
  16. 2026-07-20 17:03 UTCEPSS rescore
  17. 2026-07-20 17:03 UTCEPSS rescore
  18. 2026-07-15 16:54 UTCEPSS rescore
  19. 2026-07-15 16:54 UTCEPSS rescore
  20. 2026-07-15 01:56 UTCEPSS rescore
  21. 2026-07-13 22:26 UTCEPSS rescore
  22. 2026-07-11 08:23 UTCEPSS rescore
  23. 2026-07-04 06:27 UTCEPSS rescore
  24. 2026-07-01 15:02 UTCEPSS rescore
  25. 2026-06-27 03:05 UTCEPSS rescore
Show 39 more
  1. 2026-06-25 13:46 UTCEPSS rescore
  2. 2026-06-23 21:30 UTCEPSS rescore
  3. 2026-06-21 01:57 UTCEPSS rescore
  4. 2026-06-21 01:56 UTCEPSS rescore
  5. 2026-06-16 17:49 UTCEPSS rescore
  6. 2026-06-16 17:49 UTCEPSS rescore
  7. 2026-06-15 17:44 UTCEPSS rescore
  8. 2026-06-14 23:14 UTCEPSS rescore
  9. 2026-06-12 23:08 UTCEPSS rescore
  10. 2026-06-11 13:56 UTCEPSS rescore
  11. 2026-06-10 13:18 UTCEPSS rescore
  12. 2026-06-05 22:44 UTCEPSS rescore
  13. 2026-06-05 22:44 UTCEPSS rescore
  14. 2026-06-05 06:08 UTCEPSS rescore
  15. 2026-06-05 06:08 UTCEPSS rescore
  16. 2026-06-02 20:10 UTCEPSS rescore
  17. 2026-06-02 20:10 UTCEPSS rescore
  18. 2026-06-01 13:49 UTCEPSS rescore
  19. 2026-06-01 13:49 UTCEPSS rescore
  20. 2026-05-31 22:28 UTCEPSS rescore
  21. 2026-05-31 22:28 UTCEPSS rescore
  22. 2026-05-31 00:14 UTCEPSS rescore
  23. 2026-05-31 00:14 UTCEPSS rescore
  24. 2026-05-29 13:41 UTCEPSS rescore
  25. 2026-05-29 13:41 UTCEPSS rescore
  26. 2026-05-28 22:28 UTCEG score recompute
  27. 2026-05-28 22:28 UTCGHSA enrichment
  28. 2026-05-27 13:38 UTCEPSS rescore
  29. 2026-05-27 13:38 UTCEPSS rescore
  30. 2026-05-26 07:16 UTCEPSS rescore
  31. 2026-05-26 07:16 UTCEPSS rescore
  32. 2026-05-22 21:15 UTCEPSS rescore
  33. 2026-05-22 21:15 UTCEPSS rescore
  34. 2026-05-22 21:15 UTCEPSS rescore
  35. 2026-05-21 22:39 UTCEPSS rescore
  36. 2026-05-20 22:37 UTCEPSS rescore
  37. 2026-05-20 22:37 UTCEPSS rescore
  38. 2026-05-18 21:29 UTCEPSS rescore
  39. 2026-05-18 21:29 UTCEPSS rescore

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 Exploit-DB entry). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Exploit-DBEDB-26886✓ verified
    First seen Jul 16, 2013

    Squid 3.3.5 - Denial of Service (PoC)

    Open source ↗

Related CVEs(same CWE)

Frequently asked(4)

What is CVE-2013-4123?
CVE-2013-4123 is a medium vulnerability published on September 16, 2013. clientsiderequest.cc in Squid 3.2.x before 3.2.13 and 3.3.x before 3.3.8 allows remote attackers to cause a denial of service via a crafted port number in a HTTP Host header.
When was CVE-2013-4123 disclosed?
CVE-2013-4123 was first published in the National Vulnerability Database on September 16, 2013, with the most recent update on April 29, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2013-4123 actively exploited?
CVE-2013-4123 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 80% probability of exploitation in the next 30 days, which ranks it in the top 0.4% of all scored CVEs.
How do I remediate CVE-2013-4123?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2013-4123, 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.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2013-4123

Explore →

Is Your Infrastructure Affected by CVE-2013-4123?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs