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CVE-2026-74989

Mozilla Firefox buffer overflow

9.8 CRITICALEPSS 0.57%
  1. Published18 Aug 2026

Description

Internally found bugs present in Thunderbird 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154 and Thunderbird 154.

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< 154.0.0
Mozilla Thunderbird< 154.0

Remediation

Fixed in
Mozilla Firefox≥ 154.0.0
Mozilla Thunderbird≥ 154.0

References

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Frequently asked

Is CVE-2026-74989 being actively exploited?

CVE-2026-74989 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.57%.

How severe is CVE-2026-74989?

CVE-2026-74989 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 0.57% probability of exploitation.

Which products are affected by CVE-2026-74989?

Affected products include Mozilla Firefox, Mozilla Thunderbird.

How do I fix CVE-2026-74989?

Upgrade affected software to a fixed version, for example Mozilla Firefox 154.0.0, Mozilla Thunderbird 154.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-74989 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.