What is CVE-2026-20504?

CVE-2026-20504 is In Modem, there is a possible system crash due to a missing bounds check. The supplied enrichment data classifies it as Unclassified mapped to CWE-617 CWE-617.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Active exploitation is not confirmed from current sources for CVE-2026-20504. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-20504 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

4 public PoC repositories reported; 0 marked weaponized in current dataset. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with Not reported where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-20504 using CVSS null, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

public exploit

CVE-2026-20504

CVE-2026-20504 — In Modem, there is a possible system crash due to a missing bounds check

In Modem, there is a possible system crash due to a missing bounds check. 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: MOLY00755024; Issue ID: MSV-7865.

Published Sep 7, 2026Updated Sep 7, 2026Sources: NVD, MediaTek, Inc. (CNA), GitHub, GitHub Security Advisory, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Exploit code

public exploit, none observed

EPSS

ahead of 0% of scored CVEs

Affects

MediaTek, Inc.

19 products listed

CVSS base

Unscored

no source published a base score

Remediation

The vendor's own words where we have them.

Upgrade MediaTek chipset to a fixed release. Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
MediaTek, Inc.	MediaTek chipset	MT2735	Vulnerable
MediaTek, Inc.	MediaTek chipset	MT6833	Vulnerable
MediaTek, Inc.	MediaTek chipset	MT6853	Vulnerable
MediaTek, Inc.	MediaTek chipset	MT6855	Vulnerable
MediaTek, Inc.	MediaTek chipset	MT6873	Vulnerable
MediaTek, Inc.	MediaTek chipset	MT6875	Vulnerable
MediaTek, Inc.	MediaTek chipset	MT6877	Vulnerable
MediaTek, Inc.	MediaTek chipset	MT6880	Vulnerable
MediaTek, Inc.	MediaTek chipset	MT6883	Vulnerable
MediaTek, Inc.	MediaTek chipset	MT6885	Vulnerable
MediaTek, Inc.	MediaTek chipset	MT6889	Vulnerable
MediaTek, Inc.	MediaTek chipset	MT6890	Vulnerable

What this weakness leads to

MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.

MITRE

CWE-617 · Reachable Assertion

DoS: Crash, Exit, or Restart

Mitigation: Make sensitive open/close operation non reachable by directly user-controlled data (e.g. open/close resources)

Weakness & attack patterns

CWE-617

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Monitor for scanner or exploit-pattern traffic after 4 public PoC repositories were reported.

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Initial · CVE published
Sep 7, 2026 · NVD
Added · GHSA-p2x2-q5j5-2mj9 published (unknown)
Sep 7, 2026 · GitHub Security Advisory
CVE published by MITRE.
Sep 7, 2026 · SOCRadar CTI

References

3 on the record

www.mediatek.com/product-security-bulletin/September-2026
Vendor Advisory
nvd.nist.gov/vuln/detail/CVE-2026-20504
NVD
github.com/advisories/GHSA-p2x2-q5j5-2mj9
Exploit, Third Party Advisory

Elsewhere on this site

MediaTek, Inc.every CVE for this vendor
Unclassifiedsame class
CWE-617other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-20504 is In Modem, there is a possible system crash due to a missing bounds check, a unscored vulnerability affecting MediaTek chipset from MediaTek, Inc.. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-20504. Public exploit evidence is: 4 public PoC repositories reported; 0 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS null describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.