CVE-2021-24114Public exploitNetwork attack vector

Account takeover via trusted attachment preview URL

Published Feb 25, 2021 · Updated Aug 3, 2024

Information disclosure in Microsoft Teams for iOS allows remote authenticated users to steal Skype tokens through a crafted chat image preview. The client treats an attacker-controlled previewUrl as trusted and sends the token in the Authentication header when fetching the image. An attacker must participate in the chat and wait for the recipient to view the image; the leaked token permits account takeover.

CVSS severity5.7
Medium
EPSS probability3.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Information disclosure in Microsoft Teams for iOS allows remote authenticated users to steal Skype tokens through a crafted chat image preview. The client treats an attacker-controlled previewUrl as trusted and sends the token in the Authentication header when fetching the image. An attacker must participate in the chat and wait for the recipient to view the image; the leaked token permits account takeover.

The record

CVE
CVE-2021-24114
Published
Feb 25, 2021
Updated
Aug 3, 2024
Vendor
Microsoft
Product
Microsoft Teams for iOS
Classifications
T1528
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 25, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=2.0.0 <publication

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Microsoft · Microsoft Teams for iOSversion=2.0.0 <publication

Published CVSS scores

3.5NIST NVDAV:N/AC:M/Au:S/C:P/I:N/A:N
5.7Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1528Steal Application Access Token

Public exploit references

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo