CVE-2021-41133: Sandbox bypass via recent VFS-manipulating syscalls
Noroxi assessment
Priority: Monitor (action score 31/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.43% (FIRST EPSS).
- Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
- Fixed version: flatpak (AlmaLinux:8) 1.8.5-4.el8_4, 1.8.5-5.el8_5; flatpak-devel (AlmaLinux:8) 1.8.5-5.el8_5; flatpak-libs (AlmaLinux:8) 1.8.5-4.el8_4, 1.8.5-5.el8_5.
- Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).
Low priority for now. Upgrade to flatpak (AlmaLinux:8) 1.8.5-4.el8_4, 1.8.5-5.el8_5; flatpak-devel (AlmaLinux:8) 1.8.5-5.el8_5; flatpak-libs (AlmaLinux:8) 1.8.5-4.el8_4, 1.8.5-5.el8_5 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
Flatpak is a system for building, distributing, and running sandboxed desktop applications on Linux. In versions prior to 1.10.4 and 1.12.0, Flatpak apps with direct access to AF_UNIX sockets such as those used by Wayland, Pipewire or pipewire-pulse can trick portals and other host-OS services into treating the Flatpak app as though it was an ordinary, non-sandboxed host-OS process. They can do this by manipulating the VFS using recent mount-related syscalls that are not blocked by Flatpak's denylist seccomp filter, in order to substitute a crafted `/.flatpak-info` or make that file disappear entirely. Flatpak apps that act as clients for AF_UNIX sockets such as those used by Wayland, Pipewire or pipewire-pulse can escalate the privileges that the corresponding services will believe the Flatpak app has. Note that protocols that operate entirely over the D-Bus session bus (user bus), system bus or accessibility bus are not affected by this. This is due to the use of a proxy process `xdg-dbus-proxy`, whose VFS cannot be manipulated by the Flatpak app, when interacting with these buses. Patches exist for versions 1.10.4 and 1.12.0, and as of time of publication, a patch for version 1.8.2 is being planned. There are no workarounds aside from upgrading to a patched version.
- Published
- Oct 8, 2021
- Updated
- Jun 17, 2026
- EPSS
- 0.4% · 38th percentile
- CWE
- CWE-20
Report tools
Action score
31
Monitor
Low priority for now.
- CVSS
- 31 / 40 · 7.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.4%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 7.8
- CNA · GitHub_M
- 8.8
- 1.0 point gap
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| flatpak | flatpak | cpe:2.3:a:flatpak:flatpak |
| debian | debian linux | cpe:2.3:o:debian:debian_linux |
| fedoraproject | fedora | cpe:2.3:o:fedoraproject:fedora |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- debian debian linux11.0
- fedoraproject fedora33
- fedoraproject fedora34
- flatpak flatpakbefore 1.8.2
- flatpak flatpak1.10.0 and later · before 1.10.4
- flatpak flatpak1.11.1 and later · before 1.12.1
Versions reported by the vendor
Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.
flatpak flatpak
- >= 1.8.0, <= 1.8.2, >= 1.10.0, < 1.10.4, >= 1.11.0, < 1.12.0affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:8 | flatpak | before 1.8.5-4.el8_4 | 1.8.5-4.el8_4 |
| AlmaLinux:8 | flatpak | before 1.8.5-5.el8_5 | 1.8.5-5.el8_5 |
| AlmaLinux:8 | flatpak-devel | before 1.8.5-5.el8_5 | 1.8.5-5.el8_5 |
| AlmaLinux:8 | flatpak-libs | before 1.8.5-4.el8_4 | 1.8.5-4.el8_4 |
| AlmaLinux:8 | flatpak-libs | before 1.8.5-5.el8_5 | 1.8.5-5.el8_5 |
| AlmaLinux:8 | flatpak-selinux | before 1.8.5-4.el8_4 | 1.8.5-4.el8_4 |
| AlmaLinux:8 | flatpak-selinux | before 1.8.5-5.el8_5 | 1.8.5-5.el8_5 |
| AlmaLinux:8 | flatpak-session-helper | before 1.8.5-4.el8_4 | 1.8.5-4.el8_4 |
| AlmaLinux:8 | flatpak-session-helper | before 1.8.5-5.el8_5 | 1.8.5-5.el8_5 |
| Alpine:v3.14 | flatpak | from 1.10.0 · before 1.10.5-r0 | 1.10.5-r0 |
| Alpine:v3.15 | flatpak | from 1.10.0 · before 1.12.2-r0 | 1.12.2-r0 |
| Debian:11 | flatpak | before 1.10.5-0+deb11u1 | 1.10.5-0+deb11u1 |
| Debian:12 | flatpak | before 1.12.1-1 | 1.12.1-1 |
| openSUSE:Leap 15.2 | flatpak | before 1.10.5-lp152.3.9.1 | 1.10.5-lp152.3.9.1 |
| openSUSE:Leap 15.3 | flatpak | before 1.10.5-4.9.1 | 1.10.5-4.9.1 |
| openSUSE:Tumbleweed | flatpak | before 1.12.1-1.1 | 1.12.1-1.1 |
| Red Hat:enterprise_linux:7::client | flatpak | before 0:1.0.9-12.el7_9 | 0:1.0.9-12.el7_9 |
| Red Hat:enterprise_linux:7::client | flatpak-builder | before 0:1.0.0-12.el7_9 | 0:1.0.0-12.el7_9 |
| Red Hat:enterprise_linux:7::client | flatpak-debuginfo | before 0:1.0.9-12.el7_9 | 0:1.0.9-12.el7_9 |
| Red Hat:enterprise_linux:7::client | flatpak-devel | before 0:1.0.9-12.el7_9 | 0:1.0.9-12.el7_9 |
| Red Hat:enterprise_linux:7::client | flatpak-libs | before 0:1.0.9-12.el7_9 | 0:1.0.9-12.el7_9 |
| Red Hat:enterprise_linux:8::appstream | flatpak | before 0:1.8.5-4.el8_4 | 0:1.8.5-4.el8_4 |
| Red Hat:enterprise_linux:8::appstream | flatpak-debuginfo | before 0:1.8.5-4.el8_4 | 0:1.8.5-4.el8_4 |
| Red Hat:enterprise_linux:8::appstream | flatpak-debugsource | before 0:1.8.5-4.el8_4 | 0:1.8.5-4.el8_4 |
+25
Same product
flatpak: all recordsOther highest-scoring records for the same primary product.
- CVE-2024-42472Flatpak may allow access to files outside sandbox for certain apps40Plan
- CVE-2026-34078Flatpak has a complete sandbox escape leading to host file access and code execution in the host context38Monitor
- CVE-2019-10063Flatpak before 1.0.8, 1.1.x and 1.2.x before 1.2.4, and 1.3.x before 1.3.1 allows a sandbox bypass.37Monitor
Published before and after this one in the same product
- ← EarlierCVE-2021-21261Jan 14, 2021 · Flatpak sandbox escape via spawn portal35Monitor
- ← EarlierCVE-2021-21381Mar 11, 2021 · Sandbox escape via special tokens in .desktop file32Monitor
- Later →CVE-2021-43860Jan 12, 2022 · Permissions granted to applications can be hidden from the user at install time34Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| almalinux:flatpak | 1.8.5-5.el8_5 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:flatpak-devel | 1.8.5-5.el8_5 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:flatpak-libs | 1.8.5-5.el8_5 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:flatpak-selinux | 1.8.5-5.el8_5 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:flatpak-session-helper | 1.8.5-5.el8_5 · AlmaLinux:8 | Package registry (OSV) |
| alpine:flatpak | 1.10.5-r0 · Alpine:v3.14 | Package registry (OSV) |
| debian:flatpak | 1.12.1-1 · Debian:12 | Package registry (OSV) |
| opensuse:flatpak | 1.10.5-lp152.3.9.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| red hat:flatpak | 0:1.8.5-4.el8_4 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:flatpak-builder | 0:1.0.0-12.el7_9 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:flatpak-debuginfo | 0:1.8.5-4.el8_4 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:flatpak-debugsource | 0:1.8.5-4.el8_4 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:flatpak-devel | 0:1.0.9-12.el7_9 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:flatpak-libs | 0:1.8.5-4.el8_4 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:flatpak-libs-debuginfo | 0:1.8.5-4.el8_4 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:flatpak-selinux | 0:1.8.5-4.el8_4 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:flatpak-session-helper | 0:1.8.5-4.el8_4 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:flatpak-session-helper-debuginfo | 0:1.8.5-4.el8_4 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| red hat:flatpak-tests-debuginfo | 0:1.8.5-4.el8_4 · Red Hat:enterprise_linux:8::appstream | Package registry (OSV) |
| rocky linux:flatpak | 0:1.8.5-4.el8_4 · Rocky Linux:8 | Package registry (OSV) |
| suse:flatpak | 1.10.5-4.9.1 · SUSE:Linux Enterprise Module for Desktop Applications 15 SP2 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
No history yet (it accumulates with the daily EPSS job).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-21-0896 · Nov 8, 2021(RedHat Güvenlik Güncellemesi)
Technical details
Attack conditions
- Someone with local access to the system can trigger it.
- A low-privileged account is enough.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-20 · Improper Input ValidationCVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- Buffer Overflow via Environment VariablesCAPEC-10likelihood: High · High
- Server Side Include (SSI) InjectionCAPEC-101likelihood: High · High
- Cross Zone ScriptingCAPEC-104likelihood: Medium · High
- Command Line Execution through SQL InjectionCAPEC-108likelihood: Low · Very High
- Object Relational Mapping InjectionCAPEC-109likelihood: Low · High
- SQL Injection through SOAP Parameter TamperingCAPEC-110likelihood: High · Very High
- Double EncodingCAPEC-120likelihood: Low · Medium
- Subverting Environment Variable ValuesCAPEC-13likelihood: High · Very High
ATT&CK techniques
- Obfuscated Files or InformationT1027
- Masquerading: Invalid Code SignatureT1036.001
- Steal Web Session CookieT1539
- Subvert Trust Controls: Code SigningT1553.002
- Impair Defenses:Impair Command History LoggingT1562.003
- Hijack Execution Flow:Dynamic Linker HijackingT1574.006
- Hijack Execution Flow:Path Interception by PATH Environment VariableT1574.007
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (13 more)Show less
- github.com/flatpak/flatpak/commit/1330662f33a55e88bfe18e76de28b7922d91a999
- github.com/flatpak/flatpak/commit/26b12484eb8a6219b9e7aa287b298a894b2f34ca
- github.com/flatpak/flatpak/commit/462fca2c666e0cd2b60d6d2593a7216a83047aaf
- github.com/flatpak/flatpak/commit/4c34815784e9ffda5733225c7d95824f96375e36
- github.com/flatpak/flatpak/commit/89ae9fe74c6d445bb1b3a40e568d77cf5de47e48
- github.com/flatpak/flatpak/commit/9766ee05b1425db397d2cf23afd24c7f6146a69f
- github.com/flatpak/flatpak/commit/a10f52a7565c549612c92b8e736a6698a53db330
- github.com/flatpak/flatpak/commit/e26ac7586c392b5eb35ff4609fe232c52523b2cf
- github.com/flatpak/flatpak/security/advisories/GHSA-67h7-w3jq-vh4q
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/R5656ONDP2MGKIJMKEC7N2NXCV27WGTC/
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/T5DKCYRC6MFSTFCUP4DELCOUUP3SFEFX/
- security.gentoo.org/glsa/202312-12
- www.debian.org/security/2021/dsa-4984
Vendor advisories and official records. Exploit/PoC links are deliberately left out.