CVE-2026-53899

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreHIGH 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
Trending — 3 sources updated this week
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(high)
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 18× in last 7d / 60× 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. 2026-07-06 23:16 UTCEG score recompute
  2. 2026-07-06 23:16 UTCGHSA enrichment
  3. 2026-07-05 20:12 UTCEG score recompute
  4. 2026-07-05 20:12 UTCGHSA enrichment
  5. 2026-07-04 21:46 UTCEG score recompute
  6. 2026-07-04 21:46 UTCGHSA enrichment
  7. 2026-07-04 06:31 UTCEPSS rescore
  8. 2026-07-04 06:31 UTCEPSS rescore
  9. 2026-07-03 23:21 UTCEG score recompute
  10. 2026-07-03 23:21 UTCGHSA enrichment
  11. 2026-07-03 00:56 UTCEG score recompute
  12. 2026-07-03 00:56 UTCGHSA enrichment
  13. 2026-07-02 02:31 UTCEG score recompute
  14. 2026-07-02 02:31 UTCGHSA enrichment
  15. 2026-07-01 15:07 UTCEPSS rescore
  16. 2026-07-01 04:06 UTCEG score recompute
  17. 2026-07-01 04:06 UTCGHSA enrichment
  18. 2026-06-30 23:22 UTCEPSS rescore
  19. 2026-06-30 05:40 UTCEG score recompute
  20. 2026-06-30 05:40 UTCGHSA enrichment
  21. 2026-06-29 14:06 UTCEPSS rescore
  22. 2026-06-29 14:06 UTCEPSS rescore
  23. 2026-06-29 07:13 UTCEG score recompute
  24. 2026-06-29 07:13 UTCGHSA enrichment
  25. 2026-06-28 14:07 UTCEPSS rescore
Show 35 more
  1. 2026-06-28 08:41 UTCEG score recompute
  2. 2026-06-28 08:41 UTCGHSA enrichment
  3. 2026-06-27 10:16 UTCEG score recompute
  4. 2026-06-27 10:16 UTCGHSA enrichment
  5. 2026-06-27 03:08 UTCEPSS rescore
  6. 2026-06-26 11:51 UTCEG score recompute
  7. 2026-06-26 11:51 UTCGHSA enrichment
  8. 2026-06-25 13:49 UTCEPSS rescore
  9. 2026-06-25 08:50 UTCEG score recompute
  10. 2026-06-25 08:50 UTCGHSA enrichment
  11. 2026-06-24 14:05 UTCEPSS rescore
  12. 2026-06-24 10:25 UTCEG score recompute
  13. 2026-06-24 10:25 UTCGHSA enrichment
  14. 2026-06-23 21:33 UTCEPSS rescore
  15. 2026-06-23 21:33 UTCEPSS rescore
  16. 2026-06-23 11:58 UTCEG score recompute
  17. 2026-06-23 11:58 UTCGHSA enrichment
  18. 2026-06-22 13:32 UTCEG score recompute
  19. 2026-06-22 13:31 UTCGHSA enrichment
  20. 2026-06-21 15:03 UTCEG score recompute
  21. 2026-06-21 15:02 UTCGHSA enrichment
  22. 2026-06-21 14:56 UTCEPSS rescore
  23. 2026-06-21 14:56 UTCEPSS rescore
  24. 2026-06-21 01:59 UTCEPSS rescore
  25. 2026-06-21 01:59 UTCEPSS rescore
  26. 2026-06-20 16:26 UTCEG score recompute
  27. 2026-06-20 16:25 UTCGHSA enrichment
  28. 2026-06-19 17:57 UTCEG score recompute▲ 6.50
  29. 2026-06-19 17:56 UTCGHSA enrichment
  30. 2026-06-18 17:52 UTCEPSS rescore
  31. 2026-06-18 17:52 UTCEPSS rescore
  32. 2026-06-17 17:53 UTCEPSS rescore
  33. 2026-06-16 17:47 UTCNVD updateCVSS v3 → 6.5 · severity → MEDIUM
  34. 2026-06-16 13:47 UTCEG score recompute
  35. 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

Explore the affected products and dependency analysis for CVE-2026-53899

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