CVE-2020-5753
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 · uneditedSignal Private Messenger Android v4.59.0 and up and iOS v3.8.1.5 and up allows a remote non-contact to ring a victim's Signal phone and disclose currently used DNS server due to ICE Candidate handling before call is answered or declined.
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 · moderate confidenceSignal Private Messenger contains an information disclosure vulnerability where the app handles ICE (Interactive Connectivity Establishment) candidates before a call is answered or declined. A remote attacker who is not in the victim's contacts can initiate a call and capture ICE candidate information, which exposes the victim's currently used DNS server. This occurs because the ICE candidate exchange happens during the ringing phase, prior to user interaction.
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<= 4.59.0<= 3.8.1.5CVSS 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
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
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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Check Signal version on AndroidGo to Signal Settings > About > Version, or check the app package info in system settingsAffected if Version is 4.59.0 or lower on Android devices
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Check Signal version on iOSGo to Signal Settings > General > About, or check the App Store listingAffected if Version is 3.8.1.5 or lower on iOS devices
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Verify call handling behaviorInitiate a call from a number not in your contacts and observe the network traffic during the ringing phase using a packet capture tool. Look for STUN packets containing ICE candidates before answering or decliningAffected if ICE candidate packets are transmitted to the caller during the ringing phase (before user interaction)
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Confirm DNS exposure via ICE candidatesExamine captured STUN binding requests from the callee during incoming call ringing. The 'mapped-address' attribute reveals the DNS server used by the device's network interfaceAffected if The mapped address in STUN responses reveals DNS server information before the call is answered
A user is affected if Signal Private Messenger is installed at version 4.59.0 or below on Android, or 3.8.1.5 or below on iOS, and the app transmits ICE candidates during the ringing phase to callers not in the contact list.
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 dataUsers should update Signal Private Messenger to versions newer than Android v4.59.0 and iOS v3.8.1.5 once patches are released by Signal. No network-level mitigation is available as the issue is in the application-layer protocol handling.
- Consultation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-5753 — 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-2020-5753 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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- 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