CVE-2026-0889
Published: 13 January 2026
Summary
CVE-2026-0889 is a high-severity Uncontrolled Resource Consumption (CWE-400) vulnerability in Mozilla Firefox. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 6.5th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
Threat & Defense at a Glance
Threat & Defense Details
Likely Mitigating ControlsAI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Limiting concurrent sessions directly prevents uncontrolled resource consumption by capping the number of active sessions per user or account.
Analysis identifies uncontrolled resource consumption indicative of denial-of-service or abuse attempts.
Contingency plan testing includes resource exhaustion scenarios to verify recovery, making it harder for attackers to sustain exploits that cause uncontrolled consumption.
Updated contingency plans include current procedures to detect, contain, and recover from resource exhaustion, limiting an attacker's ability to sustain impact from uncontrolled consumption.
Alternate site allows resumption of operations if resource exhaustion at the primary site is exploited to cause unavailability.
Alternate telecommunications services enable resumption of essential functions when primary services become unavailable due to uncontrolled resource consumption.
The team can analyze and respond to resource exhaustion incidents, reducing the impact of attacks that exploit uncontrolled consumption weaknesses.
Timely maintenance support and spare parts enable rapid recovery from failures induced by uncontrolled resource consumption, shortening the impact window of denial-of-service attacks.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Direct exploitation of the described vulnerability (CWE-400 uncontrolled resource consumption in browser Service Workers) enables an adversary to crash or impair the target application, matching T1499.004 Application or System Exploitation for endpoint denial of service.
NVD Description
Denial-of-service in the DOM: Service Workers component. This vulnerability was fixed in Firefox 147 and Thunderbird 147.
Deeper analysisAI
CVE-2026-0889 is a denial-of-service vulnerability in the DOM Service Workers component of Mozilla Firefox and Thunderbird. It affects versions of these browsers prior to Firefox 147 and Thunderbird 147, in which the issue was fixed. Published on 2026-01-13, the vulnerability carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and is classified under CWE-400 (Uncontrolled Resource Consumption).
Unauthenticated remote attackers can exploit this vulnerability over the network with low attack complexity and without requiring user interaction or privileges. Exploitation results in a denial of service, causing high-impact disruption to availability while having no effect on confidentiality or integrity.
Mozilla advisories detail the patch in Firefox 147 and Thunderbird 147, recommending immediate updates to mitigate the issue. Additional technical details are available in Mozilla Foundation Security Advisory 2026-01 and 2026-04, along with Bugzilla entry 1999084.
Details
- CWE(s)