CVE-2026-53899

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

Score 6.5 from GitHub Security Advisory published 2026-06-16. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
6.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 6.5Exploit: NoneExposed: 0

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

Firefox for iOS used partial domain matching when attaching cookies to PDF requests, allowing a malicious site on a suffix domain to receive cookies belonging to the target site. This vulnerability was fixed in Firefox for iOS 152.0.

CVSS v3
6.5
EG Score
6.5(medium)
EG Risk
34(Track)
EG Risk 34/100SSVC: 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
Severity65% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
0.9%
KEV
Not listed

Published

June 16, 2026

Last Modified

June 17, 2026

Advisory Details (2)

Auto-updated Jun 16, 2026
No patch confirmed yet.
generic

Security Vulnerabilities fixed in Firefox for iOS 152.0 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-56/
generic

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=2042909

Vendor Advisories for CVE-2026-53899(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 6× in last 7d / 51× 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. 2026-07-24 14:18 UTCEPSS rescore
  2. 2026-07-23 14:18 UTCEPSS rescore
  3. 2026-07-23 03:19 UTCEG score recompute
  4. 2026-07-22 14:08 UTCEPSS rescore
  5. 2026-07-20 17:08 UTCEPSS rescore
  6. 2026-07-18 10:04 UTCEPSS rescore
  7. 2026-07-16 17:03 UTCEPSS rescore
  8. 2026-07-16 14:39 UTCGHSA enrichment
  9. 2026-07-15 16:57 UTCEPSS rescore
  10. 2026-07-15 16:57 UTCEPSS rescore
  11. 2026-07-15 15:32 UTCGHSA enrichment
  12. 2026-07-14 12:43 UTCGHSA enrichment
  13. 2026-07-13 22:31 UTCEPSS rescore
  14. 2026-07-13 14:16 UTCGHSA enrichment
  15. 2026-07-12 15:43 UTCGHSA enrichment
  16. 2026-07-12 05:46 UTCEPSS rescore
  17. 2026-07-11 17:04 UTCGHSA enrichment
  18. 2026-07-11 08:27 UTCEPSS rescore
  19. 2026-07-11 08:27 UTCEPSS rescore
  20. 2026-07-10 18:38 UTCGHSA enrichment
  21. 2026-07-09 19:56 UTCGHSA enrichment
  22. 2026-07-09 19:10 UTCEPSS rescore
  23. 2026-07-09 19:10 UTCEPSS rescore
  24. 2026-07-08 20:09 UTCGHSA enrichment
  25. 2026-07-08 15:16 UTCEPSS rescore
Show 46 more
  1. 2026-07-08 15:16 UTCEPSS rescore
  2. 2026-07-07 21:41 UTCGHSA enrichment
  3. 2026-07-07 13:46 UTCEPSS rescore
  4. 2026-07-07 13:46 UTCEPSS rescore
  5. 2026-07-06 23:16 UTCGHSA enrichment
  6. 2026-07-05 20:12 UTCGHSA enrichment
  7. 2026-07-04 21:46 UTCGHSA enrichment
  8. 2026-07-04 06:31 UTCEPSS rescore
  9. 2026-07-04 06:31 UTCEPSS rescore
  10. 2026-07-03 23:21 UTCGHSA enrichment
  11. 2026-07-03 00:56 UTCGHSA enrichment
  12. 2026-07-02 02:31 UTCGHSA enrichment
  13. 2026-07-01 15:07 UTCEPSS rescore
  14. 2026-07-01 04:06 UTCGHSA enrichment
  15. 2026-06-30 23:22 UTCEPSS rescore
  16. 2026-06-30 05:40 UTCGHSA enrichment
  17. 2026-06-29 14:06 UTCEPSS rescore
  18. 2026-06-29 14:06 UTCEPSS rescore
  19. 2026-06-29 07:13 UTCGHSA enrichment
  20. 2026-06-28 14:07 UTCEPSS rescore
  21. 2026-06-28 08:41 UTCGHSA enrichment
  22. 2026-06-27 10:16 UTCGHSA enrichment
  23. 2026-06-27 03:08 UTCEPSS rescore
  24. 2026-06-26 11:51 UTCGHSA enrichment
  25. 2026-06-25 13:49 UTCEPSS rescore
  26. 2026-06-25 08:50 UTCGHSA enrichment
  27. 2026-06-24 14:05 UTCEPSS rescore
  28. 2026-06-24 10:25 UTCGHSA enrichment
  29. 2026-06-23 21:33 UTCEPSS rescore
  30. 2026-06-23 21:33 UTCEPSS rescore
  31. 2026-06-23 11:58 UTCGHSA enrichment
  32. 2026-06-22 13:31 UTCGHSA enrichment
  33. 2026-06-21 15:02 UTCGHSA enrichment
  34. 2026-06-21 14:56 UTCEPSS rescore
  35. 2026-06-21 14:56 UTCEPSS rescore
  36. 2026-06-21 01:59 UTCEPSS rescore
  37. 2026-06-21 01:59 UTCEPSS rescore
  38. 2026-06-20 16:25 UTCGHSA enrichment
  39. 2026-06-19 17:57 UTCEG score recompute▲ 6.50
  40. 2026-06-19 17:56 UTCGHSA enrichment
  41. 2026-06-18 17:52 UTCEPSS rescore
  42. 2026-06-18 17:52 UTCEPSS rescore
  43. 2026-06-17 17:53 UTCEPSS rescore
  44. 2026-06-16 17:47 UTCNVD updateCVSS v3 → 6.5 · severity → MEDIUM
  45. 2026-06-16 13:47 UTCEG score recompute
  46. 2026-06-16 13:46 UTCNVD updatefirst tracked

Frequently asked(5)

What is CVE-2026-53899?
CVE-2026-53899 is a medium vulnerability published on June 16, 2026. Firefox for iOS used partial domain matching when attaching cookies to PDF requests, allowing a malicious site on a suffix domain to receive cookies belonging to the target site. This vulnerability was fixed in Firefox for iOS 152.0.
When was CVE-2026-53899 disclosed?
CVE-2026-53899 was first published in the National Vulnerability Database on June 16, 2026, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-53899 actively exploited?
CVE-2026-53899 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-53899?
CVE-2026-53899 has a CVSS v3.1 base score of 6.5 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-53899?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-53899, 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

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