CVE-2020-5753Network attack vector

DNS server disclosure via pre-answer ICE resolution

Published May 20, 2020 · Updated Aug 4, 2024

Information disclosure in Signal for Android and iOS allows remote attackers to identify a callee's DNS server before a call is answered. The pre-answer WebRTC signaling path resolves attacker-supplied domain names in ICE candidates, exposing the resolver to an attacker-controlled authoritative name server. Possession of the callee's Signal number is sufficient; the disclosure reveals coarse location or network changes and, with EDNS Client Subnet, part of the callee's IP address.

CVSS severity5.3
Medium
EPSS probability1.07%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in Signal for Android and iOS allows remote attackers to identify a callee's DNS server before a call is answered. The pre-answer WebRTC signaling path resolves attacker-supplied domain names in ICE candidates, exposing the resolver to an attacker-controlled authoritative name server. Possession of the callee's Signal number is sufficient; the disclosure reveals coarse location or network changes and, with EDNS Client Subnet, part of the callee's IP address.

The record

CVE
CVE-2020-5753
Published
May 20, 2020
Updated
Aug 4, 2024
Vendor
Signal
Product
Signal
Classifications
CWE-670, T1592
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 20, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Android versions v4.59.0 and up, iOS versions v3.8.1.5 and up

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Signal · Signalversion=Android versions v4.59.0 and up, iOS versions v3.8.1.5 and up

Published CVSS scores

3.3TenableAV:N/AC:L/Au:N/C:P/I:N/A:N
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-670Always-Incorrect Control Flow Implementation
T1592Gather Victim Host Information

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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