Firefox: Cleartext Transmission of Sensitive Information
CVE-2025-5270 is a high-severity cleartext transmission of sensitive information vulnerability in Firefox from Mozilla, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. There is no confirmed exploitation so far. EPSS estimates a 0.29% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of Firefox you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on mozilla.org for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Mozilla | Firefox | Not specified in the record | Not stated |
| Mozilla | Thunderbird | Not specified in the record | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- NoneNothing can be modified.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. Scored by CISA (ADP).
Official 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: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Cleartext Transmission of Sensitive Information
The product transmits sensitive or security-critical data in cleartext in a communication channel that can be sniffed by unauthorized actors.
How developers prevent this class of flaw
- Before transmitting, encrypt the data using reliable, confidentiality-protecting cryptographic protocols.
- When using web applications with SSL, use SSL for the entire session from login to logout, not just for the initial login page.
- When designing hardware platforms, ensure that approved encryption algorithms (such as those recommended by NIST) protect paths from security critical data to trusted user applications.
More Cleartext Transmission of Sensitive Information vulnerabilities (CWE-319)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other references
- bugzilla.mozilla.org/show_bug.cgi?id=1910298Permissions Required
Other vulnerabilities in Firefox
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
Recent Cleartext Transmission of Sensitive Information vulnerabilities
- 9.1 Critical severity
- 10.0 Critical severity
- 8.7 High severity
- 7.5 High severity
- 9.0 Critical severity
- 7.5 High severity
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