CVE-2025-5270 | SNI was sometimes unencrypted

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.

Published: 2025-05-27 Last update: 2026-04-13 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-5270 is rated Moderate Risk (43.4/100): CVSS High severity, with low exploitation likelihood (EPSS 0.17%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-5270

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-03-23 0.02% 0.17% +0.15%
2 2025-05-28 — 0.02% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-5270

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2025-5270

OS Trackers for CVE-2025-5270

vendor priority summary link
alpine — CVE-2025-5270: 1 source package rows (firefox); 145 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 145. https://security.alpinelinux.org/vuln/CVE-2025-5270
debian not yet assigned CVE-2025-5270 not yet assigned priority: Debian including 1 source packages (firefox), 1 status rows across 1 suites (sid): resolved 1. https://security-tracker.debian.org/tracker/CVE-2025-5270
redhat low — https://access.redhat.com/security/cve/CVE-2025-5270
suse high — https://www.suse.com/security/cve/CVE-2025-5270/
ubuntu medium CVE-2025-5270 medium priority: Ubuntu including 9 source packages (firefox, mozjs102, …), 65 status rows across 8 suites (bionic, focal, jammy, noble, oracular, plucky, questing, upstream): DNE 35, ignored 10, needs-triage 9, not-affected 9, released 2. https://ubuntu.com/security/CVE-2025-5270

Affected software / configurations for CVE-2025-5270

Vendor Product Version Raw CPE
mozilla firefox < 139.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*

References for CVE-2025-5270

cvelogic Threat Intelligence