CVE-2021-39658
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedismsEx service is a vendor service in unisoc equipment。ismsEx service is an extension of sms system service，but it does not check the permissions of the caller，resulting in permission leaks。Third-party apps can use this service to arbitrarily modify and set system properties。Product: AndroidVersions: Android SoCAndroid ID: A-207479207
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe ismsEx vendor service in Unisoc Android SoC equipment lacks permission validation on callers, allowing any third-party application to bypass Android's permission model and arbitrarily modify or set system properties through this SMS system service extension.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE dataall versionsCVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify the device SoC manufacturerCheck /proc/cpuinfo or use 'getprop ro.hardware' or 'getprop ro.chipname' to determine the processor/soc vendor. Unisoc may appear as 'sprd' or 'unisoc' in these properties.Affected if The device uses a Unisoc (formerly Spreadtrum) SoC processor
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Check if ismsEx service is presentRun 'dumpsys ismsEx' or check for the service in 'dumpsys' output. The vulnerable service is a vendor-specific SMS extension service.Affected if The ismsEx service is available on the device (indicating a Unisoc Android device with this vendor service)
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Verify service permission configurationRun 'dumpsys package ismsEx' or inspect the service definition in the vendor's framework JAR. Check if the service declares android.permission.INTERACT_ACROSS_USERS or lacks proper permission checks.Affected if The service lacks permission validation or allows access without android.permission.SEND_SMS
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Confirm Android version and security patch levelCheck 'getprop ro.build.version.security_patch' and 'getprop ro.build.version.release' to document the device state.Affected if Device is on any Android version (all versions are affected per vendor scope) and has not received a Unisoc/OEM firmware patch for this issue
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Test for unauthenticated service accessUse 'service list' to confirm ismsEx is registered as a system service, then attempt to observe if any app can bind to it without holding SMS permissions.Affected if The ismsEx service is exposed to third-party apps without permission enforcement
A device is affected if it uses a Unisoc SoC and contains the ismsEx vendor service without having received the corresponding firmware-level security patch from Unisoc or the device OEM.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataThis is a firmware-level vulnerability requiring a patch from Unisoc (the SoC vendor) or the device OEM; users should monitor for and apply security updates from their device vendor.
- Consultation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,096.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-39658 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-39658 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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