CVE-2021-39789
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 · uneditedIn Telecom, there is a possible leak of TTY mode change due to a missing permission check. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-12LAndroid ID: A-203880906
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 confidenceA missing permission check in Android's Telecom component allows local attackers to modify TTY (Text Telephone) mode settings without proper authorization, leading to local privilege escalation. The vulnerability requires no user interaction or additional execution privileges.
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 data= 12.1CVSS 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
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/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.
-
Check Android versionNavigate to Settings > About Phone > Android version or run 'getprop ro.build.version.release' via ADB shellAffected if Version is exactly 12.1 (Android 12.1)
-
Check security patch levelNavigate to Settings > About Phone > Security patch level or run 'getprop ro.build.version.security_patch' via ADB shellAffected if Patch level is earlier than February 2022 (2022-02-01) or the field is empty/unknown on Android 12.1 devices
-
Verify Telecom component TTY authorizationInspect Telecom service logs for permission checks when modifying TTY settings using 'dumpsys telecom' via ADB shell, looking for TTY mode change operationsAffected if No permission check is enforced when TTY mode is modified (vulnerable state)
-
Check TTY mode configurationRun 'settings get global preferred_tty_mode' via ADB shell to check current TTY settingAffected if Any value returns successfully without permission denial (on Android 12.1 with old patch)
A device is affected if running Android 12.1 with a security patch level before February 2022 and the Telecom component allows TTY mode changes without authorization checks.
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.
dbcve · scopedApply the Android-12L system security update (patch level February 2022 or later) from device manufacturers. No user-facing configuration change can mitigate this; the fix requires platform-level code changes.
Android-12L with January 2022 security patch level or later
- 1. Apply the Android security update for January 2022 or later to your Android-12L device.
- 2. Verify the patch has been applied by checking Settings > About Phone > Android version or Security patch level.
- 3. Confirm the Security patch level shows a date of January 2022 or later.
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-39789 — 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-2021-39789 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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
- No spam, self-promotion, credentials, or personal data