CVE-2021-21381Public exploit

Host file access via unchecked desktop tokens

Published Mar 11, 2021 · Updated Aug 3, 2024

File-access bypass in Flatpak 0.9.4 through 1.10.1 allows attackers to expose user-readable host files via a malicious app. The desktop-file export path accepts literal @@ or @@u tokens in an app's Exec field, so file forwarding treats following paths as user-selected files and grants the sandbox access. Exploitation requires installation of the crafted app; access is limited to files readable by the account running it.

CVSS severity7.1
High
EPSS probability1.55%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

File-access bypass in Flatpak 0.9.4 through 1.10.1 allows attackers to expose user-readable host files via a malicious app. The desktop-file export path accepts literal @@ or @@u tokens in an app's Exec field, so file forwarding treats following paths as user-selected files and grants the sandbox access. Exploitation requires installation of the crafted app; access is limited to files readable by the account running it.

The record

CVE
CVE-2021-21381
Published
Mar 11, 2021
Updated
Aug 3, 2024
Vendor
Flatpak
Product
Flatpak
Classifications
CWE-74, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 11, 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=>= 0.9.4, < 1.10.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Flatpak · Flatpakversion=>= 0.9.4, < 1.10.2

Published CVSS scores

5.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:N
8.2NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
7.1GitHub, Inc.CVSS:3.1/AV:L/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.

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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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
T1204.002User Execution: Malicious File

Public exploit references

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

Technologies

Your stack

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Your stack

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