Firefox: Improper Handling of Faults that Lead to Instruction Skips
CVE-2025-8028 is a critical-severity improper handling of faults that lead to instruction skips vulnerability in Firefox from Mozilla, with a CVSS 3.1 base score of 9.8 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 0.58% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
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
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CISA (ADP).
Official description
On arm64, a WASM `br_table` instruction with a lot of entries could lead to the label being too far from the instruction causing truncation and incorrect computation of the branch address. This vulnerability was fixed in Firefox 141, Firefox ESR 115.26, Firefox ESR 128.13, Firefox ESR 140.1, Thunderbird 141, Thunderbird 128.13, and Thunderbird 140.1.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Handling of Faults that Lead to Instruction Skips
The device is missing or incorrectly implements circuitry or sensors that detect and mitigate the skipping of security-critical CPU instructions when they occur.
How developers prevent this class of flaw
- Design strategies for ensuring safe failure if inputs, such as Vcc, are modified out of acceptable ranges.
- Design strategies for ensuring safe behavior if instructions attempt to be skipped.
- Identify mission critical secrets that should be wiped if faulting is detected, and design a mechanism to do the deletion.
More Improper Handling of Faults that Lead to Instruction Skips vulnerabilities (CWE-1332)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- mozilla.org/security/advisories/mfsa2025-56/
- mozilla.org/security/advisories/mfsa2025-57/
- mozilla.org/security/advisories/mfsa2025-58/
- mozilla.org/security/advisories/mfsa2025-59/
- mozilla.org/security/advisories/mfsa2025-61/
- mozilla.org/security/advisories/mfsa2025-62/
- mozilla.org/security/advisories/mfsa2025-63/
Other references
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
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