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CVE Record

CVE-2026-34078: Flatpak has a complete sandbox escape leading to host file access and code execution in the host context

Flatpak is a Linux application sandboxing and distribution framework. Prior to 1.16.4, the Flatpak portal accepts paths in the sandbox-expose options which can be app-controlled symlinks pointing at arbitrary paths. Flatpak run mounts the resolved host path in the sandbox. This gives apps access to all host files and can be used as a primitive to gain code execution in the host context. This vulnerability is fixed in 1.16.4.

CriticalCVSS 9.3Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

CVE-2026-34078 breaks Flatpak’s isolation. A malicious or compromised Flatpak app could make Flatpak expose arbitrary host paths into its sandbox, allowing access to host files and potentially code execution outside the sandbox. Flatpak versions before 1.16.4 are affected.

Executive priority

Treat this as urgent for Linux desktop or workstation fleets using Flatpak. The issue undermines a core security boundary and has critical severity, but current sources do not prove active exploitation.

Technical view

Before Flatpak 1.16.4, sandbox-expose options accepted app-controlled symlink paths. Flatpak resolved and mounted the host target into the sandbox, creating CWE-59/CWE-61 path-link handling exposure with high confidentiality, integrity, and availability impact.

Likely exposure

Linux systems using Flatpak versions earlier than 1.16.4 are the exposed population. Risk is higher where users can install or run untrusted Flatpak apps, or where Flatpak is relied on as a containment boundary for desktop applications.

Exploitation context

The provided sources do not show CISA KEV listing or confirmed active exploitation. They do describe a complete sandbox escape primitive with host file access and host-context code execution potential, so absence of exploitation evidence should not lower remediation urgency.

Researcher notes

Focus validation on symlink handling around sandbox-expose portal options and host path mounting behavior. Avoid assuming every distribution is vulnerable at the same package version because vendors may ship backported fixes.

Mitigation direction

  • Upgrade Flatpak to 1.16.4 or a vendor-fixed backport.
  • Apply relevant Red Hat security advisories where applicable.
  • Prioritize endpoints that allow untrusted Flatpak app installation.
  • Limit Flatpak app sources to trusted repositories until patched.
  • Monitor vendor guidance for distribution-specific package status.

Validation and detection

  • Inventory installed Flatpak package versions across Linux endpoints.
  • Confirm Flatpak is 1.16.4 or vendor-marked fixed.
  • Check Red Hat CVE and errata status for affected fleets.
  • Review systems where Flatpak is used for application isolation.
  • Track CISA KEV and vendor advisories for exploit-status changes.
Prepared
Confidence
high
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-59: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-61: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
description · low confidence lookup

Execution behavior lookup

The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
description · low confidence lookup

Privilege behavior lookup

The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-34078 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9.3 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
3ADP providers
16Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9.3CVSS 4.0CriticalCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N——GitHub_M
9CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H2.36redhat-SADP

Vulnerability scoring details

Base CVSS 4.0 score

9.3Critical
CVSS 4.0 vector shape for CVE-2026-34078Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container
redhat-SADPflatpak: Flatpak: Arbitrary code execution via crafted symlinks in sandbox-expose options
other:Red Hat severity ratingcvssV3_1
  • 2026-04-07T22:01:09.203Z: Reported to Red Hat.
  • 2026-04-07T21:27:45.643Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
flatpakflatpak< 1.16.4Listed
Weakness

CWE details

CWE-59CWE-61

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-59 · source CWE mapping

Improper Link Resolution Before File Access ('Link Following')

Improper Link Resolution Before File Access ('Link Following') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-61 · source CWE mapping

UNIX Symbolic Link (Symlink) Following

UNIX Symbolic Link (Symlink) Following represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs