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CVE-2021-43817

21
FAUCET Score

CVE-2021-43817 is a reflected Cross-Site Scripting (XSS) vulnerability affecting Collabora Online versions prior to 6.4.16 and 4.2.20. An attacker could inject unescaped HTML during iframe creation, allowing script execution within the Collabora Online iframe context. This medium severity vulnerability (CVSS 6.1) has a network attack vector and low attack complexity, potentially leading to the compromise of limited user settings and session authentication tokens. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 4.2.20CPE matchmatch criteria
cpe:2.3:a:collabora:online:*:*:*:*:*:*:*:*
>= 6.4.0, < 6.4.16CPE matchmatch criteria
cpe:2.3:a:collabora:online:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.2HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
4.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.65%
Probability of exploitation in next 30 days
EPSS Percentile
47.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0065 is in the 51st percentile among its peer group of 26,221 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

github.com / CollaboraOnline/online/security/advisories/GHSA-7f6h-v9mx-58q9
Third Party Advisory