CVE-2026-8950
Published: May 19, 2026· Updated: May 20, 2026
Official Description
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.
Risk Analysis
This critical vulnerability in Mozilla Firefox and Thunderbird allows for a same-origin policy bypass in the Networking: HTTP component. With a CVSS score of 9.3, this flaw poses a high risk, as it could enable attackers to access sensitive information across different origins. The EPSS score is currently unavailable, so the likelihood of exploitation is unknown.
No public exploit is currently known for this vulnerability. Its network attack vector and low attack complexity suggest it is remotely exploitable, requiring user interaction.
To address this vulnerability, users should upgrade to Firefox 151, Firefox ESR 140.11, Thunderbird 151, or Thunderbird 140.11. Keeping browser and email client software updated is vital for security.
Technical Analysis
CVE-2026-8950 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.
A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), with a CVSS base score of 9.3.
The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
Official Patches & Advisories
All References (5)
Quick Facts
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2026-8950 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts