Data stored in cookies for non-HTML content while browsing Incognito could be viewed after closing private tabs

published 2025-09-30 13 mo ago modified 2026-10-05 35 d ago also EUVD-2025-31731

cvss: 4.0; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.1%; EPSS 0.1% chance of exploitation in 30 days, percentile 1%
public exploits: 0; none known

Cookie storage for non-HTML temporary documents was being shared incorrectly with normal browsing content, allowing information from private tabs to escape Incognito mode even after the user closed all tabs. This vulnerability was fixed in Firefox for iOS 143.1.

Patch / fix

fixed in 1

mozilla firefox 143.1

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 13 mo ago (2025-09-30)

Exploit prediction

0.12% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	4.0	CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
CNA	3.1	4.0	CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected products

Mozilla Firefox for iOS

Classification

Weakness

CWE-359 Exposure of Private Personal Information to an Unauthorized Actor

References

mozilla.org /security/advisories/mfsa2025-79/
vendor-advisory
bugzilla.mozilla.org /show_bug.cgi?id=1684624
issue-tracking, permissions-required

Sources

CVE List CVE-2025-10859
NVD CVE-2025-10859

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary