CVE-2026-96808 (GCVE-0-2026-96808)

Vulnerability from cvelistv5 – Published: 2026-09-23 16:58 – Updated: 2026-09-23 18:22
VLAI
Summary
In Flatpak before 1.18.1, the revokefs writer, used by the flatpak-system-helper to receive repository data from unprivileged callers, validated file paths by rejecting literal .. components but did not prevent symlink traversal. A malicious local user in an active local session could obtain two revokefs sessions via the system helper, create a symlink in one session pointing into the other session's directory, and retain a file descriptor through that symlink. This allowed the attacker to modify files belonging to a different revokefs session after they had been validated and imported by the system helper. In particular, an attacker could use this to tamper with ostree commit objects in the system repository after they passed signature verification, enabling root-controlled file writes to attacker-chosen paths and local root privilege escalation.
Severity
7.4 (High)
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-23 18:22 UTC
CWE
  • CWE-61 - UNIX Symbolic Link (Symlink) Following
Assigner
mitre CNA under the mitre root
CNA scorecard E 29/100 over 2146 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Flatpak Flatpak Affected: 0 , < 1.18.1 (semver)
    cpe:2.3:a:flatpak:flatpak:*:*:*:*:*:*:*:*
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Solutions

CNA · mitre
Fixed in 1.18.1 by commits: * a3583bc https://github.com/flatpak/flatpak/commit/a3583bc87d4f86c2794ff879ea56fce95b0b0b5f "revokefs: Avoid symlink path traversal out of basefd in simple cases" * b00c7b5 https://github.com/flatpak/flatpak/commit/b00c7b5073a25bdc34653642de543b5ef6fe0225 "revokefs: Avoid symlink path traversal in link(), rename()" * 4ddb5dc https://github.com/flatpak/flatpak/commit/4ddb5dc0de1bd25e52627f520a49063d94f79377 "revokefs: Avoid symlink path traversal in symlink()" * e7f96b4 https://github.com/flatpak/flatpak/commit/e7f96b4d1533f735ace2ea21dbf770e8d4be465a "revokefs: Avoid symlink path traversal in chmod()" For LTS operating system distributions, backports of these changes are available in the flatpak-1.16.x branch.

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How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

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