CVE-2021-43817Network attack vector

Session-token theft via unescaped iframe variable

Published Dec 13, 2021 · Updated Aug 4, 2024

Reflected XSS in Collabora Online before 4.2.20 and 6.0.0 through 6.4.15 allows remote attackers to steal session tokens via crafted iframes. During iframe creation, attacker-controlled HTML is copied into a variable without escaping and runs as script in the Collabora Online iframe context. Victim interaction is required; the script can read browser-stored settings and the authentication token passed when the session iframe is created.

CVSS severity8.2
High
EPSS probability0.65%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in Collabora Online before 4.2.20 and 6.0.0 through 6.4.15 allows remote attackers to steal session tokens via crafted iframes. During iframe creation, attacker-controlled HTML is copied into a variable without escaping and runs as script in the Collabora Online iframe context. Victim interaction is required; the script can read browser-stored settings and the authentication token passed when the session iframe is created.

The record

CVE
CVE-2021-43817
Published
Dec 13, 2021
Updated
Aug 4, 2024
Vendor
Collabora Productivity
Product
Collabora Online
Classifications
CWE-79, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 13, 2021CVE 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=< 4.2.20
  2. Affected versionversion=>= 6.0.0, < 6.4.16

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Collabora Productivity · Collabora Onlineversion=< 4.2.20; version=>= 6.0.0, < 6.4.16

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
8.2GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/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

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
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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