CVE-2021-1799Network attack vector

Restricted-port access via redirect validation bypass

Published Apr 2, 2021 · Updated Aug 3, 2024

WebRTC in Apple iOS and iPadOS before 14.4 and macOS Big Sur before 11.2 allows malicious websites to access restricted server ports. The WebRTC redirect path fails to enforce restricted-port validation after redirection, although Apple has not disclosed the affected function or exact validation sequence. A user must load attacker-controlled web content; the resulting requests can alter data or actions on a reachable server, with no reported code execution on the Apple device.

CVSS severity6.5
Medium
EPSS probability1.76%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

WebRTC in Apple iOS and iPadOS before 14.4 and macOS Big Sur before 11.2 allows malicious websites to access restricted server ports. The WebRTC redirect path fails to enforce restricted-port validation after redirection, although Apple has not disclosed the affected function or exact validation sequence. A user must load attacker-controlled web content; the resulting requests can alter data or actions on a reachable server, with no reported code execution on the Apple device.

The record

CVE
CVE-2021-1799
Published
Apr 2, 2021
Updated
Aug 3, 2024
Vendor
Apple
Product
iOS and iPadOS
Classifications
T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 2, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=unspecified <14.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Apple · iOS and iPadOSversion=unspecified <14.4
Apple · macOSversion=unspecified <11.2; version=unspecified <14.0; version=unspecified <14.4; version=unspecified <7.3

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1189Drive-by Compromise

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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