CVE-2015-4521

HIGHCVSS v2 · 7.57.5—
EchelonGraph scoreLOW confidence

This CVE was only ever scored under CVSS v2.0. NVD CVSS v2.0 base 7.5 — v2 rates that HIGH (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: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 3.5% 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
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 3%CVSS v2: 7.5Exploit: None knownExposed: 0

A fix is available — apply it.

The ConvertDialogOptions function in Mozilla Firefox before 41.0 and Firefox ESR 38.x before 38.3 might allow remote attackers to cause a denial of service (memory corruption and application crash) or possibly have unspecified other impact via unknown vectors.

CVSS v2.0 (legacy)
7.5HIGHNVD never assigned a CVSS v3 rating to this CVE
EG Score
7.5(low)
EG Risk
40(Track)
EG Risk 40/100SSVC: 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
Severity75% × 45%
Exploitation4% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
3%
EPSS %ILE
88%
KEV
Not listed

Published

September 24, 2015

Last Modified

May 6, 2026

References (40)

Patch Availability(4)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuthunderbird (1:38.3.0+build1-0ubuntu0.12.04.1) @ precise2026-05-22ubuntu
ubuntufirefox (41.0+build3-0ubuntu0.15.04.1) @ vivid2026-05-22ubuntu
redhatthunderbird-0:38.3.0-1.el7_12015-10-01redhat
redhatfirefox-0:38.3.0-2.ael7b_12015-09-22redhat

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.

Affected Packages

(2 across 2 ecosystems)
Debian:7(1)
PackageVulnerable rangeFixed inDependents
iceweasel10.0.12esr-1 ... 38.2.1esr-1~deb8u1 (165 versions)38.3.0esr-1~deb7u1—
Debian:8(1)
PackageVulnerable rangeFixed inDependents
iceweasel31.6.0esr-1 ... 38.3.0esr-1~deb7u1 (44 versions)38.3.0esr-1~deb8u1—

All Vendor Advisories

(4)

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 / 24× 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 113 total refreshes for this CVE.

  1. 2026-08-20 22:50 UTCEPSS rescore
  2. 2026-08-19 16:59 UTCEPSS rescore
  3. 2026-08-18 13:43 UTCEPSS rescore
  4. 2026-08-16 14:51 UTCEPSS rescore
  5. 2026-08-16 02:09 UTCEPSS rescore
  6. 2026-08-15 01:25 UTCEPSS rescore
  7. 2026-08-12 13:46 UTCEPSS rescore
  8. 2026-08-09 13:42 UTCEPSS rescore
  9. 2026-08-08 16:31 UTCEPSS rescore
  10. 2026-08-07 16:22 UTCEPSS rescore
  11. 2026-08-06 13:42 UTCEPSS rescore
  12. 2026-08-05 19:12 UTCEPSS rescore
  13. 2026-08-04 15:04 UTCEPSS rescore
  14. 2026-08-02 02:22 UTCEPSS rescore
  15. 2026-08-01 04:11 UTCEPSS rescore
  16. 2026-07-30 16:23 UTCEPSS rescore
  17. 2026-07-30 01:26 UTCEPSS rescore
  18. 2026-07-28 15:31 UTCEPSS rescore
  19. 2026-07-26 14:50 UTCEPSS rescore
  20. 2026-07-26 13:54 UTCEG score recompute▲ 7.50
  21. 2026-07-24 14:13 UTCEPSS rescore
  22. 2026-07-23 14:14 UTCEPSS rescore
  23. 2026-07-23 01:18 UTCEG score recompute
  24. 2026-07-23 00:20 UTCEG score recompute
  25. 2026-07-22 21:58 UTCEG score recompute
Show 75 more
  1. 2026-07-22 14:04 UTCEPSS rescore
  2. 2026-07-21 15:21 UTCEPSS rescore
  3. 2026-07-21 15:21 UTCEPSS rescore
  4. 2026-07-20 17:03 UTCEPSS rescore
  5. 2026-07-19 14:27 UTCEPSS rescore
  6. 2026-07-19 14:27 UTCEPSS rescore
  7. 2026-07-19 02:26 UTCEPSS rescore
  8. 2026-07-19 02:26 UTCEPSS rescore
  9. 2026-07-18 10:00 UTCEPSS rescore
  10. 2026-07-16 16:59 UTCEPSS rescore
  11. 2026-07-16 16:59 UTCEPSS rescore
  12. 2026-07-15 16:54 UTCEPSS rescore
  13. 2026-07-15 16:54 UTCEPSS rescore
  14. 2026-07-15 01:56 UTCEPSS rescore
  15. 2026-07-13 22:26 UTCEPSS rescore
  16. 2026-07-12 05:42 UTCEPSS rescore
  17. 2026-07-11 08:23 UTCEPSS rescore
  18. 2026-07-09 19:05 UTCEPSS rescore
  19. 2026-07-08 15:10 UTCEPSS rescore
  20. 2026-07-06 16:24 UTCEPSS rescore
  21. 2026-07-06 02:20 UTCEPSS rescore
  22. 2026-07-05 02:26 UTCEPSS rescore
  23. 2026-07-04 06:27 UTCEPSS rescore
  24. 2026-07-02 15:21 UTCEPSS rescore
  25. 2026-07-01 15:02 UTCEPSS rescore
  26. 2026-07-01 15:02 UTCEPSS rescore
  27. 2026-06-30 23:19 UTCEPSS rescore
  28. 2026-06-30 23:19 UTCEPSS rescore
  29. 2026-06-29 14:03 UTCEPSS rescore
  30. 2026-06-28 04:53 UTCEPSS rescore
  31. 2026-06-27 03:05 UTCEPSS rescore
  32. 2026-06-25 13:47 UTCEPSS rescore
  33. 2026-06-25 13:47 UTCEPSS rescore
  34. 2026-06-24 14:02 UTCEPSS rescore
  35. 2026-06-24 14:02 UTCEPSS rescore
  36. 2026-06-23 21:30 UTCEPSS rescore
  37. 2026-06-22 14:23 UTCEPSS rescore
  38. 2026-06-22 14:22 UTCEPSS rescore
  39. 2026-06-21 01:57 UTCEPSS rescore
  40. 2026-06-21 01:57 UTCEPSS rescore
  41. 2026-06-19 19:23 UTCEPSS rescore
  42. 2026-06-19 19:23 UTCEPSS rescore
  43. 2026-06-18 17:50 UTCEPSS rescore
  44. 2026-06-18 17:49 UTCEPSS rescore
  45. 2026-06-17 17:49 UTCEPSS rescore
  46. 2026-06-16 17:50 UTCEPSS rescore
  47. 2026-06-16 17:49 UTCEPSS rescore
  48. 2026-06-15 17:45 UTCEPSS rescore
  49. 2026-06-14 23:14 UTCEPSS rescore
  50. 2026-06-13 22:57 UTCEPSS rescore
  51. 2026-06-12 23:09 UTCEPSS rescore
  52. 2026-06-11 13:57 UTCEPSS rescore
  53. 2026-06-10 22:15 UTCEPSS rescore
  54. 2026-06-08 14:14 UTCEPSS rescore
  55. 2026-06-07 15:22 UTCEPSS rescore
  56. 2026-06-06 13:45 UTCEPSS rescore
  57. 2026-06-05 22:44 UTCEPSS rescore
  58. 2026-06-04 13:10 UTCEPSS rescore
  59. 2026-06-04 13:09 UTCEPSS rescore
  60. 2026-06-02 20:10 UTCEPSS rescore
  61. 2026-06-02 20:10 UTCEPSS rescore
  62. 2026-06-01 13:49 UTCEPSS rescore
  63. 2026-06-01 13:49 UTCEPSS rescore
  64. 2026-05-31 22:28 UTCEPSS rescore
  65. 2026-05-31 22:28 UTCEPSS rescore
  66. 2026-05-31 22:28 UTCEPSS rescore
  67. 2026-05-31 00:14 UTCEPSS rescore
  68. 2026-05-29 13:41 UTCEPSS rescore
  69. 2026-05-28 13:42 UTCEPSS rescore
  70. 2026-05-28 13:42 UTCEPSS rescore
  71. 2026-05-27 13:38 UTCEPSS rescore
  72. 2026-05-27 13:38 UTCEPSS rescore
  73. 2026-05-26 07:16 UTCEPSS rescore
  74. 2026-05-26 07:16 UTCEPSS rescore
  75. 2026-05-24 16:43 UTCEPSS rescore

Frequently asked(4)

What is CVE-2015-4521?
CVE-2015-4521 is a high vulnerability published on September 24, 2015. The ConvertDialogOptions function in Mozilla Firefox before 41.0 and Firefox ESR 38.x before 38.3 might allow remote attackers to cause a denial of service (memory corruption and application crash) or possibly have unspecified other impact via unknown vectors.
When was CVE-2015-4521 disclosed?
CVE-2015-4521 was first published in the National Vulnerability Database on September 24, 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-2015-4521 actively exploited?
CVE-2015-4521 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 3% probability of exploitation in the next 30 days, which ranks it in the top 11.8% of all scored CVEs.
How do I remediate CVE-2015-4521?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2015-4521, 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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