CVE-2026-8950

⛔ critical

Summary

Same-origin policy bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

CVSS Score

9.3

Critical

EPSS Score

0.0

Exploit Probability

Published Date

2026-05-19

First Seen: 2026-05-20

📊 Relative Risk Intelligence

This CVE is High Risk - more severe than 88.7% of all 365,863 vulnerabilities in our database.

#41,473

Top 25% most severe

Severity Percentile

🎯 CISA SSVC Assessment Updated: May 19, 2026

🔍 Exploitation Status

None

No known exploits

⚙️ Automatable

Requires human interaction

💥 Technical Impact

Partial

Limited system impact

🏆 Discovered By

Jakub Szymsza

SSVC data provided by CISA

Last Modified 2026-05-20

Source NVD 🔗

CVSS Vector 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

CWE IDs (Weakness Types)

CWE-346

📦 Affected Products 4

Vendor	Product	Status	Affected Versions
mozilla	firefox	Affected	< 140.11.0
mozilla	firefox	Affected	< 151.0.0
mozilla	thunderbird	Affected	< 140.11
mozilla	thunderbird	Affected	< 151.0.0

🔗 References 5

https://bugzilla.mozilla.org/show_bug.cgi?id=1965430

Permissions Required

https://www.mozilla.org/security/advisories/mfsa2026...

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026...

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026...

Vendor Advisory

https://www.mozilla.org/security/advisories/mfsa2026...

Vendor Advisory

🔗 Related CVEs 6

CVE ID	Severity	CVSS	EPSS	Summary	Published
CVE-2026-100756	⚠️ high	8.1	0.3	Incorrect boundary conditions in the Audio/Video: Playback component. This vulnerability was fixed in Firefox ESR 153.4,...	2026-09-29
CVE-2026-100767	⚠️ high	8.8	0.3	Use-after-free in the Networking: Cache component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, T...	2026-09-29
CVE-2026-100768	⚠️ high	8.8	0.3	Use-after-free in the Graphics: WebGPU component. This vulnerability was fixed in Thunderbird 157 and Firefox 157.	2026-09-29
CVE-2026-100769	⚠️ high	8.8	0.3	Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird ...	2026-09-29
CVE-2026-100770	⛔ critical	9.6	0.3	Sandbox escape due to use-after-free in the DOM: Content Processes component. This vulnerability was fixed in Firefox ES...	2026-09-29
CVE-2026-100771	⚠️ high	8.1	0.3	Undefined behavior in the DOM: Streams component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Th...	2026-09-29

These CVEs affect the same products