MT2735, MT6833, MT6833P, MT6853, MT6853T…: Reachable Assertion
CVE-2025-20666 is a high-severity reachable assertion vulnerability in MT2735, MT6833, MT6833P, MT6853, MT6853T, MT6855, MT6855T, MT6873, MT6875, MT6875T, MT6877, MT6877T, MT6877TT, MT6880, MT6883, MT6885, MT6889, MT6890, MT6891, MT6893, MT8666, MT8667, MT8673, MT8675, MT8771, MT8791, MT8791T, MT8795T, MT8797, MT8798 from MediaTek, 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. Affected MT2735, MT6833, MT6833P, MT6853, MT6853T, MT6855, MT6855T, MT6873, MT6875, MT6875T, MT6877, MT6877T, MT6877TT, MT6880, MT6883, MT6885, MT6889, MT6890, MT6891, MT6893, MT8666, MT8667, MT8673, MT8675, MT8771, MT8791, MT8791T, MT8795T, MT8797, MT8798 versions: Modem NR15. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.84% chance of exploitation within 30 days, higher than 58% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of MT2735, MT6833, MT6833P, MT6853, MT6853T, MT6855, MT6855T, MT6873, MT6875, MT6875T, MT6877, MT6877T, MT6877TT, MT6880, MT6883, MT6885, MT6889, MT6890, MT6891, MT6893, MT8666, MT8667, MT8673, MT8675, MT8771, MT8791, MT8791T, MT8795T, MT8797, MT8798 you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on corp.mediatek.com 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 |
|---|---|---|---|
| MediaTek | MT2735, MT6833, MT6833P, MT6853, MT6853T, MT6855, MT6855T, MT6873, MT6875, MT6875T, MT6877, MT6877T, MT6877TT, MT6880, MT6883, MT6885, MT6889, MT6890, MT6891, MT6893, MT8666, MT8667, MT8673, MT8675, MT8771, MT8791, MT8791T, MT8795T, MT8797, MT8798 | Modem NR15 | Not stated |
| MediaTek | Nr15 | 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
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.5 | High | NVD |
| CVSS 3.1 | 6.5 | Medium | CISA (ADP) |
Official description
In Modem, there is a possible system crash due to an uncaught exception. This could lead to remote denial of service, if a UE has connected to a rogue base station controlled by the attacker, with no additional execution privileges needed. User interaction is not needed for exploitation. Patch ID: MOLY00650610; Issue ID: MSV-2933.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Reachable Assertion
The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.
How developers prevent this class of flaw
- If the assertion statement is required (e.g., for security or reliability), change the invoking code to avoid the conditions that trigger the assertion.
- Consider changing the assertion to some other less fatal error. This might not be easy to implement, since other code may be needed to handle the error.
- Make sensitive open/close operations non-reachable from directly user-controlled data (e.g. open/close resources)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Recent Reachable Assertion vulnerabilities
- 7.5 High severity
- 8.6 High severity
- 8.6 High severity
- 7.5 High severity
- 8.6 High severity
- 8.6 High severity
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