CVE-2015-5400

MEDIUMCVSS v2 · 6.86.8—
EchelonGraph scoreLOW confidence

This CVE was only ever scored under CVSS v2.0. NVD CVSS v2.0 base 6.8 — 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:M/Au:N/C:P/I:P/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 20.8% 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
Elevated
6.8EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 21%CVSS v2: 6.8Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

Squid before 3.5.6 does not properly handle CONNECT method peer responses when configured with cache_peer, which allows remote attackers to bypass intended restrictions and gain access to a backend proxy via a CONNECT request.

CVSS v2.0 (legacy)
6.8MEDIUMNVD never assigned a CVSS v3 rating to this CVE
EG Score
6.8MEDIUMlow confidence
EG Risk
51
EG Risk 51/100CISA SSVC

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
Severity68% × 45%
Exploitation40% × 40%
Automatability30% × 15%
CISA SSVC: Track at low, Track or Track* at medium and Track* or Attend at high mission impact.
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
21%
EPSS %ILE
97th
KEV
Not listed

CISA SSVCTrack at low, Track or Track* at medium and Track* or Attend at high mission impact.

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (EG-KEV: elevated) · Automatable unknown (not published for this CVE) · Technical impact unknown (not published for this CVE). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 28, 2015

Last Modified

May 6, 2026

References (30)

Affected Packages

(7 across 7 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
squid—
  • every version up to 4.1-1: fixed in 4.1-1
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
squid—
  • every version up to 4.1-1: fixed in 4.1-1
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
squid—
  • every version up to 4.1-1: fixed in 4.1-1
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
squid—
  • every version up to 4.1-1: fixed in 4.1-1
—
Debian:6.0(1)
PackageVulnerable rangeFix by version rangeDependents
squid33.1.6-1.2, 3.1.6-1.2+squeeze1, 3.1.6-1.2+squeeze2, 3.1.6-1.2+squeeze3, 3.1.6-1.2+squeeze4
  • every version up to 3.1.6-1.2+squeeze5: fixed in 3.1.6-1.2+squeeze5
—
Debian:7(1)
PackageVulnerable rangeFix by version rangeDependents
squid33.1.20-2.2, 3.1.20-2.2+deb7u1, 3.1.20-2.2+deb7u2
  • every version up to 3.1.20-2.2+deb7u3: fixed in 3.1.20-2.2+deb7u3
—
Debian:8(1)
PackageVulnerable rangeFix by version rangeDependents
squid33.4.8-6
  • every version up to 3.4.8-6+deb8u1: fixed in 3.4.8-6+deb8u1
—

Data Freshness Timeline

(refreshed 5× in last 7d / 18× 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.

Showing the most recent 100 of 141 total refreshes for this CVE.

  1. 2026-10-04 23:17 UTCEPSS rescore
  2. 2026-10-03 14:21 UTCEPSS rescore
  3. 2026-09-30 14:58 UTCEPSS rescore
  4. 2026-09-30 14:58 UTCEPSS rescore
  5. 2026-09-30 09:05 UTCEG score recompute
  6. 2026-09-27 13:40 UTCEPSS rescore
  7. 2026-09-26 15:53 UTCEPSS rescore
  8. 2026-09-26 15:53 UTCEPSS rescore
  9. 2026-09-23 13:41 UTCEPSS rescore
  10. 2026-09-19 15:35 UTCEPSS rescore
  11. 2026-09-19 08:00 UTCOSV refresh
  12. 2026-09-18 19:22 UTCEPSS rescore
  13. 2026-09-17 19:21 UTCEPSS rescore
  14. 2026-09-15 03:05 UTCEPSS rescore
  15. 2026-09-12 14:55 UTCEPSS rescore
  16. 2026-09-11 09:31 UTCEPSS rescore
  17. 2026-09-10 09:26 UTCEPSS rescore
  18. 2026-09-06 13:42 UTCEPSS rescore
  19. 2026-09-04 13:55 UTCEPSS rescore
  20. 2026-09-02 14:07 UTCEPSS rescore
  21. 2026-09-01 13:48 UTCEPSS rescore
  22. 2026-08-31 11:34 UTCOSV refresh
  23. 2026-08-27 14:20 UTCEPSS rescore
  24. 2026-08-26 14:41 UTCEPSS rescore
  25. 2026-08-25 13:44 UTCEPSS rescore
Show 75 more
  1. 2026-08-23 00:13 UTCEPSS rescore
  2. 2026-08-21 23:44 UTCEPSS rescore
  3. 2026-08-20 22:50 UTCEPSS rescore
  4. 2026-08-19 16:59 UTCEPSS rescore
  5. 2026-08-18 13:43 UTCEPSS rescore
  6. 2026-08-16 14:51 UTCEPSS rescore
  7. 2026-08-16 02:09 UTCEPSS rescore
  8. 2026-08-15 01:25 UTCEPSS rescore
  9. 2026-08-14 16:54 UTCOSV refresh
  10. 2026-08-12 13:46 UTCEPSS rescore
  11. 2026-08-11 13:36 UTCEPSS rescore
  12. 2026-08-08 16:32 UTCEPSS rescore
  13. 2026-08-07 16:22 UTCEPSS rescore
  14. 2026-08-06 13:42 UTCEPSS rescore
  15. 2026-08-05 19:12 UTCEPSS rescore
  16. 2026-08-04 15:04 UTCEPSS rescore
  17. 2026-08-04 10:31 UTCEPSS rescore
  18. 2026-07-30 05:24 UTCOSV refresh
  19. 2026-07-30 01:26 UTCEPSS rescore
  20. 2026-07-30 01:26 UTCEPSS rescore
  21. 2026-07-28 15:31 UTCEPSS rescore
  22. 2026-07-26 14:50 UTCEPSS rescore
  23. 2026-07-26 13:54 UTCEG score recompute▲ 6.80
  24. 2026-07-25 14:13 UTCEPSS rescore
  25. 2026-07-24 14:13 UTCEPSS rescore
  26. 2026-07-23 14:14 UTCEPSS rescore
  27. 2026-07-23 01:18 UTCEG score recompute
  28. 2026-07-23 00:20 UTCEG score recompute
  29. 2026-07-22 21:59 UTCEG score recompute
  30. 2026-07-22 14:04 UTCEPSS rescore
  31. 2026-07-21 15:21 UTCEPSS rescore
  32. 2026-07-21 15:21 UTCEPSS rescore
  33. 2026-07-20 17:03 UTCEPSS rescore
  34. 2026-07-19 02:26 UTCEPSS rescore
  35. 2026-07-19 02:26 UTCEPSS rescore
  36. 2026-07-18 10:00 UTCEPSS rescore
  37. 2026-07-16 16:59 UTCEPSS rescore
  38. 2026-07-15 16:54 UTCEPSS rescore
  39. 2026-07-15 16:54 UTCEPSS rescore
  40. 2026-07-15 01:56 UTCEPSS rescore
  41. 2026-07-13 22:26 UTCEPSS rescore
  42. 2026-07-13 22:26 UTCEPSS rescore
  43. 2026-07-12 14:38 UTCOSV refresh
  44. 2026-07-12 05:42 UTCEPSS rescore
  45. 2026-07-11 08:23 UTCEPSS rescore
  46. 2026-07-09 19:05 UTCEPSS rescore
  47. 2026-07-09 19:05 UTCEPSS rescore
  48. 2026-07-08 15:10 UTCEPSS rescore
  49. 2026-07-07 13:42 UTCEPSS rescore
  50. 2026-07-07 13:42 UTCEPSS rescore
  51. 2026-07-06 16:24 UTCEPSS rescore
  52. 2026-07-05 02:26 UTCEPSS rescore
  53. 2026-07-04 06:28 UTCEPSS rescore
  54. 2026-07-01 15:02 UTCEPSS rescore
  55. 2026-06-30 23:19 UTCEPSS rescore
  56. 2026-06-30 23:19 UTCEPSS rescore
  57. 2026-06-29 14:03 UTCEPSS rescore
  58. 2026-06-29 14:03 UTCEPSS rescore
  59. 2026-06-28 14:04 UTCEPSS rescore
  60. 2026-06-28 04:53 UTCEPSS rescore
  61. 2026-06-27 03:05 UTCEPSS rescore
  62. 2026-06-25 13:47 UTCEPSS rescore
  63. 2026-06-25 13:47 UTCEPSS rescore
  64. 2026-06-24 14:02 UTCEPSS rescore
  65. 2026-06-24 14:02 UTCEPSS rescore
  66. 2026-06-23 21:30 UTCEPSS rescore
  67. 2026-06-23 20:20 UTCOSV refresh
  68. 2026-06-22 14:23 UTCEPSS rescore
  69. 2026-06-22 14:23 UTCEPSS rescore
  70. 2026-06-21 01:57 UTCEPSS rescore
  71. 2026-06-21 01:57 UTCEPSS rescore
  72. 2026-06-19 19:23 UTCEPSS rescore
  73. 2026-06-19 19:23 UTCEPSS rescore
  74. 2026-06-18 17:50 UTCEPSS rescore
  75. 2026-06-17 17:50 UTCEPSS rescore

Related CVEs(same product)

Frequently asked(4)

What is CVE-2015-5400?
CVE-2015-5400 is a medium vulnerability published on September 28, 2015. Squid before 3.5.6 does not properly handle CONNECT method peer responses when configured with cache_peer, which allows remote attackers to bypass intended restrictions and gain access to a backend proxy via a CONNECT request.
When was CVE-2015-5400 disclosed?
CVE-2015-5400 was first published on September 28, 2015, 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-2015-5400 actively exploited?
CVE-2015-5400 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 21% probability of exploitation in the next 30 days (97th percentile of EPSS-scored CVEs).
How do I remediate CVE-2015-5400?
A fix for CVE-2015-5400 is available: update to the fixed version the vendor names in its advisory.

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