EUVD-2026-88553Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessObtain local unprivileged account on host
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ExploitLocate world-accessible /var/tmp/flatpak-cache-* directory
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ExecutionRead temporary repository contents
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ImpactDisclose sensitive cached data
Vulnerability Assessment
| Weakness |
CWE
ASVS 5.0
V5 - File Handling Temp file with insecure permissions
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| Exploitation Conditions | Requires a local, unprivileged user account on a system where Flatpak (before 1.18.4) has created temporary repository cache directories under /var/tmp/flatpak-cache-* during an app or runtime download; the affected directories must exist at exploitation time and the attacker reads them before cleanup. Limiting factors: exploitation is confined to multi-user hosts (single-user desktops have little exposure), needs local access rather than network reach, and yields only whatever data resides in the transient cache - there is no privilege escalation or code execution component. |
| Impact | No CVSS vector, CWE, EPSS, KEV, or POC data is provided for CVE-2026-97026, so risk must be inferred from the advisory text alone. The fix - 'Restrict permissions on temporary repository directories in /var/tmp/flatpak-cache-*' - indicates a local information-exposure flaw (incorrect/overly-permissive default permissions, CWE-276/732) on world-readable or otherwise accessible temp cache directories used during app/runtime downloads. Because this was disclosed alongside CVE-2026-97025 (auth token leakage from OCI repositories), the temp directories plausibly contain downloaded repository data and potentially sensitive material that other local users on the same host could read. This is a local, low-severity issue: it requires a co-resident unprivileged account and yields at most confidentiality exposure, not privilege escalation or RCE. It is NOT in CISA KEV and there is no public exploit identified at time of analysis, so it is a hygiene/hardening fix rather than an urgent priority. Reported by AISLE in cooperation with Red Hat, which lends credibility, but no independent CVSS scoring exists to confirm severity - treat the local/low-impact characterization as inferred, not vendor-confirmed. |
| Exploit ScenarioDerived | On a multi-user Linux host, an unprivileged local user browses the /var/tmp/flatpak-cache-* directories created by another user's (or system) Flatpak download operation and reads their contents due to lax directory permissions, potentially exposing downloaded repository data or credentials. No public exploit code is identified; exploitation is opportunistic file reading requiring an existing local account. |
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Alert meAnalysisAIv1 – Sep 28, 2026
Incorrect permissions on temporary repository cache directories in Flatpak before 1.18.4 allow a local, unprivileged user to read data left behind in /var/tmp/flatpak-cache-* while another user's app or runtime is being downloaded from an OCI repository. Exploitation requires a pre-existing local account on a multi-user host and the transient cache directory to still exist before Flatpak cleans it up, and the result is low-confidentiality information disclosure only - no privilege escalation, code execution, or file modification is possible, and no public exploit identified at time of analysis. The same 1.18.4 release addresses several more serious sibling issues (CVE-2026-97023, CVE-2026-97024, CVE-2026-97025, CVE-2026-97027, CVE-2026-97029), so a single upgrade remediates all of them.
RemediationAI
Upgrade to Flatpak 1.18.4 or later, the vendor-released patch that addresses this issue alongside its five sibling CVEs from the same advisory (https://seclists.org/oss-sec/2026/q3/965, GHSA-r9w3-qx54-qvc8); distributions that backport should confirm the /var/tmp/flatpak-cache-* permission change is included, not just the version string. If the upgrade must be staged, reduce exposure by deleting stale /var/tmp/flatpak-cache-* directories after install or update operations - with the trade-off that this discards partially downloaded or resumable OCI content and forces re-downloads, so it should be a cleanup step rather than a deletion loop running during pulls. On multi-user hosts where local accounts are not fully trusted, treat the vulnerability as an argument for segregating untrusted users onto separate virtual machines or user namespaces rather than relying on Flatpak's cache handling, since the attacker needs only an ordinary local login and no interaction from the victim. Mount-level hardening of /var/tmp (for example restrictive mount options or a private tmpfs) is a heavier compensating control and should be evaluated carefully because many services rely on /var/tmp persisting across reboots, so breaking that assumption can cause unrelated application failures; it is best applied selectively on hosts that are already multi-user and already under the 1.18.4 baseline.
Affected ProductsAI
Flatpak versions prior to 1.18.4 running on hosts where the OCI app/runtime pull path populates temporary repository directories under /var/tmp/flatpak-cache-*; the fix ships in Flatpak 1.18.4, tracked upstream as GHSA-r9w3-qx54-qvc8 and announced in the vendor release notice referenced at https://seclists.org/oss-sec/2026/q3/965. No CPE strings or vendor CVE page are supplied in the input data, so the affected set should be read as 'Flatpak < 1.18.4 on multi-user Linux systems,' with single-user desktops effectively at negligible exposure because there is no second local account to abuse the world-readable cache. Exposure is also conditional on the transient directories existing at the moment of attack, which limits the window to active download/install operations and to installations where cleanup has not yet run. Because the same advisory bundles CVE-2026-97023, CVE-2026-97024, CVE-2026-97025, CVE-2026-97027, and CVE-2026-97029 into the 1.18.4 release, any inventory of affected systems should be treated as covering all six issues rather than CVE-2026-97026 in isolation.
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Technical ContextAI · show details
Flatpak's OCI download path stages repository data in per-operation temporary directories named /var/tmp/flatpak-cache-*, and the flaw is that these directories were created without restrictive permissions. This matters because /var/tmp follows the traditional sticky, world-writable semantics rather than per-user private directories such as /run/user/$UID or XDG_RUNTIME_DIR, so anything placed there with permissive modes is readable by every local account on the machine; the entries are transient, since Flatpak removes them once the pull completes. No CWE is assigned in the supplied data, but the failure mode is characteristic of incorrect permission assignment on shared temporary storage (the CWE-732 family): the root cause is a mode/ownership omission, not a memory-safety bug, path traversal, or authentication bypass. The assessed vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N reflects exactly that shape - local access, low privilege required, no user interaction, unchanged scope, and limited confidentiality impact with no integrity or availability component. No EPSS score, KEV entry, POC reference, or CVE-specific CVSS vector accompanies the CVE in the available data; the only source is the oss-security release notice for Flatpak 1.18.4, and the assessed risk is therefore inferred from the advisory text plus the mechanics of /var/tmp rather than from an authoritative score.
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Severity by source
AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:L
Local co-resident account required (AV:L, PR:L); overly-permissive temp directory yields confidentiality-only exposure (C:L) with no integrity or availability impact.
Primary rating from Vendor (CNA).
CVSS VectorVendor
Lifecycle Timeline
2Description PRE-NVD
Executive ViewAI
Flatpak deployments on multi-user Linux systems before 1.18.4 can expose transient OCI repository cache data to other local users, causing limited confidentiality loss. Although this CVE alone does not enable privilege escalation or code execution, the same 1.18.4 upgrade resolves several more severe sibling Flatpak vulnerabilities, making fleet-wide remediation a business priority for organizations with shared Linux environments.
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Threat Intelligence Overview
NVD
CVE.org
EPSS
Vulnrichment
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.
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Path traversal in Flatpak's app deployment handling of the exported files/etc directory allows a malicious Flatpak appli
Exploit-DB