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CVE-2025-5270— SNI was sometimes unencrypted

Quick assessment

Affected
Mozilla Firefox
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Mozilla Firefox是美国Mozilla基金会的一款开源Web浏览器。 Mozilla Firefox 139之前版本存在安全漏洞，该漏洞源于SNI可能未加密发送。

AI Predicted 5.9 Difficulty: Moderate EPSS 0.27% · P19

Possible ATT&CK Techniques 1 AI

T1557.002 · ARP Cache Poisoning
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I. Basic Information for CVE-2025-5270

Vulnerability Information
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Vulnerability Title
SNI was sometimes unencrypted
Source: CVE Program / CVE List V5
Vulnerability Description
In certain cases, SNI could have been sent unencrypted even when encrypted DNS was enabled. This vulnerability was fixed in Firefox 139 and Thunderbird 139.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Mozilla Firefox 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mozilla Firefox是美国Mozilla基金会的一款开源Web浏览器。 Mozilla Firefox 139之前版本存在安全漏洞，该漏洞源于SNI可能未加密发送。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Mozilla Firefox 139 ~ * -
Mozilla Thunderbird 139 ~ * -

II. Public POCs for CVE-2025-5270

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III. Intelligence Information for CVE-2025-5270

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Vendor Advisories for CVE-2025-5270 (2)

Same Patch Batch · Mozilla · 2025-05-27 · 11 CVEs total

CVE-2025-5272 Memory safety bugs fixed in Firefox 139 and Thunderbird 139
CVE-2025-5271 Devtools' preview ignored CSP headers
CVE-2025-5269 Memory safety bug fixed in Firefox ESR 128.11 and Thunderbird 128.11
CVE-2025-5268 Memory safety bugs fixed in Firefox 139, Thunderbird 139, Firefox ESR 128.11, and Thunderb
CVE-2025-5267 Clickjacking vulnerability could have led to leaking saved payment card details
CVE-2025-5266 Script element events leaked cross-origin resource status
CVE-2025-5264 Potential local code execution in “Copy as cURL” command
CVE-2025-5265 Potential local code execution in “Copy as cURL” command
CVE-2025-5263 Error handling for script execution was incorrectly isolated from web content
CVE-2025-5262 Mozilla Thunderbird 安全漏洞

IV. Related Vulnerabilities

Same product: Firefox
Same vendor: Mozilla

V. Comments for CVE-2025-5270

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