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CVE-2025-1020

Mozilla Firefox buffer overflow

9.8 CRITICALEPSS 0.54%
  1. Published4 Feb 2025

Description

Memory safety bugs present in Firefox 134 and Thunderbird 134. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 135 and Thunderbird 135.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Mozilla Firefox< 135.0
Mozilla Thunderbird≥ 131.0 < 135.0

Remediation

Fixed in
Mozilla Firefox≥ 135.0
Mozilla Thunderbird≥ 135.0

References

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Frequently asked

Is CVE-2025-1020 being actively exploited?

CVE-2025-1020 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.54%.

How severe is CVE-2025-1020?

CVE-2025-1020 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 0.54% probability of exploitation.

Which products are affected by CVE-2025-1020?

Affected products include Mozilla Firefox, Mozilla Thunderbird.

How do I fix CVE-2025-1020?

Upgrade affected software to a fixed version, for example Mozilla Firefox 135.0, Mozilla Thunderbird 135.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2025-1020 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.