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CVE-2026-53899

MEDIUM 6.5

Published 2026-06-16 · Last modified 2026-06-16

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.

NO EXPLOITATION SIGNALS

No known exploitation, public exploit, or elevated probability at this time. Track for changes.

Exploitation likelihood

0.1%chance of exploitation in 30 days · 1st percentile

○ In CISA KEV ○ Public exploit / PoC

Impact if exploited

6.5CVSS 3.1 · MEDIUM

  • ConfidentialityLow
  • IntegrityLow
  • AvailabilityNone

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept & exploit code

Test against your own equipment

curl -s https://vulnpedia.com/cve/CVE-2026-53899/poc.jsonMachine-readable PoC index for this CVE (for automation).

Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-53899/poc.json

Affected

Vendors Mozilla

Products Firefox For Ios Firefox Mobile

Weakness (CWE)

  • CWE-345: Insufficient Verification of Data Authenticity

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Known Affected Software Configurations

VendorProductVersion range
MozillaFirefox Mobile< 152.0

All CVSS metrics

  • MEDIUM 6.5 v3.1 · ADP Primary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
  • MEDIUM 6.5 v3.1 · NVD Secondary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

References

Advisories

Technical & other

Sources: NVD · CVE.org · EPSS