CVE-2026-96281

System-app downgrade via unprivileged remote-ref removal

Published Sep 27, 2026 · Updated Sep 27, 2026

Anti-downgrade bypass in Flatpak 1.18.0 and earlier allows local users to install older system-wide apps through an active login session. The unprivileged system-helper RemoveLocalRef method deletes an app or runtime's remote ref, leaving the anti-downgrade check without the commit date it compares. On multi-user Linux hosts, another user's launch of a downgraded app can expose that user to vulnerabilities fixed in newer releases.

CVSS severity5.4
Medium
EPSS probability0.17%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Anti-downgrade bypass in Flatpak 1.18.0 and earlier allows local users to install older system-wide apps through an active login session. The unprivileged system-helper RemoveLocalRef method deletes an app or runtime's remote ref, leaving the anti-downgrade check without the commit date it compares. On multi-user Linux hosts, another user's launch of a downgraded app can expose that user to vulnerabilities fixed in newer releases.

The record

CVE
CVE-2026-96281
Published
Sep 27, 2026
Updated
Sep 27, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.4FlatpakCVSS:4.0/AV:P/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
3.3Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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