CVE-2021-28117Network attack vector

Attack-vector chaining via unvalidated URI schemes

Published Mar 20, 2021 · Updated Oct 15, 2024

Improper URI validation in KDE Discover before 5.21.3 allows context-dependent attackers to present dangerous links in store text. KNSResource::longDescription turns any URL-like text into an href without restricting the scheme to HTTP or HTTPS. Exploitation requires control of text fetched from store.kde.org and a user click; the resulting URI launch can chain to other attack vectors.

CVSS severity7.5
High
EPSS probability1.56%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper URI validation in KDE Discover before 5.21.3 allows context-dependent attackers to present dangerous links in store text. KNSResource::longDescription turns any URL-like text into an href without restricting the scheme to HTTP or HTTPS. Exploitation requires control of text fetched from store.kde.org and a user click; the resulting URI launch can chain to other attack vectors.

The record

CVE
CVE-2021-28117
Published
Mar 20, 2021
Updated
Oct 15, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Oct 15, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
5.0NVDAV:N/AC:L/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.

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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

T1204.001User Execution Malicious Link

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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