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CVE-2021-21261

26
FAUCET Score

CVE-2021-21261 describes a sandbox escape vulnerability in Flatpak versions 0.11.4 through 1.8.4 and 1.9.x, affecting the flatpak-portal service. A malicious or compromised Flatpak application can leverage this flaw to execute arbitrary code on the host system by manipulating environment variables passed to non-sandboxed processes. This vulnerability carries a high CVSS score of 8.8, indicating a local attack vector with low complexity, allowing for high impact on confidentiality, integrity, and availability. While there is no evidence of active exploitation, public exploit code, or significant community discussion, the vulnerability is patched in Flatpak versions 1.8.5 and 1.10.0.

Impacted Technologies

VendorProductVersion(s)CPE
>= 0.11.4, < 1.8.5CPE matchmatch criteria
cpe:2.3:a:flatpak:flatpak:*:*:*:*:*:*:*:*
>= 1.9.1, < 1.10.0CPE matchmatch criteria
cpe:2.3:a:flatpak:flatpak:*:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.3HIGH

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

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.0
Impact Score
4.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.57%
Probability of exploitation in next 30 days
EPSS Percentile
43.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0057 is in the 83rd percentile among its peer group of 17,070 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.2 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (5)

github_advisorypatch availablevia nvd_reference
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: flatpak-0:1.0.9-10.el7_9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: flatpak-0:1.6.2-5.el8_3
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.1 Extended Update SupportFixed in: flatpak-0:1.0.9-3.el8_1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Extended Update SupportFixed in: flatpak-0:1.6.2-4.el8_2
View patch

Vendor Advisories (1)

redhatCVE-2021-21261Important

flatpak: sandbox escape via spawn portal

Jan 14, 2021

References

github.com / flatpak/flatpak/commit/6d1773d2a54dde9b099043f07a2094a4f1c2f486
PatchThird Party Advisory
github.com / flatpak/flatpak/commit/6e5ae7a109cdfa9735ea7ccbd8cb79f9e8d3ae8b
PatchThird Party Advisory
github.com / flatpak/flatpak/commit/aeb6a7ab0abaac4a8f4ad98b3df476d9de6b8bd4
PatchThird Party Advisory
github.com / flatpak/flatpak/commit/cc1401043c075268ecc652eac557ef8076b5eaba
Third Party Advisory
github.com / flatpak/flatpak/releases/tag/1.8.5
Third Party Advisory
github.com / flatpak/flatpak/security/advisories/GHSA-4ppf-fxf6-vxg2
Third Party Advisory
security.gentoo.org / glsa/202101-21
Third Party Advisory
debian.org / security/2021/dsa-4830
Third Party Advisory