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Full vulnerability report · 2026
CVE-2026-73611High confidence

File Browser 2.50.0 through 2.63.21 JWT Expiration Bypass

filebrowser · filebrowser

Official source article: GitHub GHSA-V3JV-RMH2-635J ↗. Check the applicable product and release in the original source.

7.6HighCVSS 4.0
Recommended action
Within 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Critical, raised one band.upgradedsince 14 Aug 2026

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • EPSS is 0.43% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs filebrowser filebrowser and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-57815

No EUVD known-exploited evidence

File Browser versions from 2.50.0 through 2.63.21 fail to validate JWT expiration when proxy authentication is configured with a non-default logout page. Attackers with a previously valid token can access protected routes and administrative endpoints indefinitely, and exchange expired tokens for fresh ones via the renewal endpoint.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
7.6 · CVSS 4.0
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

File Browser versions from 2.50.0 through 2.63.21 fail to validate JWT expiration when proxy authentication is configured with a non-default logout page. Attackers with a previously valid token can access protected routes and administrative endpoints indefinitely, and exchange expired tokens for fresh ones via the renewal endpoint.

What

File Browser versions from 2.50.0 through 2.63.21 fail to validate JWT expiration when proxy authentication is configured with a non-default logout page. Attackers with a previously valid token can access protected routes and administrative endpoints indefinitely, and exchange expired tokens for fresh ones via the renewal endpoint.

Why

According to WASC, Insufficient Session Expiration is when a web site permits an attacker to reuse old session credentials or session IDs for authorization.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

File Browser versions from 2.50.0 through 2.63.21 fail to validate JWT expiration when proxy authentication is configured with a non-default logout page. Attackers with a previously valid token can access protected routes and administrative endpoints indefinitely, and exchange expired tokens for fresh ones via the renewal endpoint.

Why

According to WASC, Insufficient Session Expiration is when a web site permits an attacker to reuse old session credentials or session IDs for authorization.

How

An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

CISA Vulnrichment records proof-of-concept exploitation in its SSVC data. BlackTree has not independently executed or validated exploit material.

Likely attack path
a network path → Insufficient Session Expiration → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
Low: a basic authenticated account is required
User interaction
None
Attack complexity
High: exploitation depends on specific conditions
Security boundary
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-613 ↗

CWE-613: Insufficient Session Expiration. According to WASC, Insufficient Session Expiration is when a web site permits an attacker to reuse old session credentials or session IDs for authorization.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Common Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.ATPresentAttack requirements: A particular deployment or execution condition must be present.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.VCHighVulnerable-system confidentiality: A successful attack can cause a major loss.VIHighVulnerable-system integrity: A successful attack can cause a major loss.VANoneVulnerable-system availability: No direct loss is represented by this metric.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.
Post-exploitation / living off the land
Stolen credentials, tokens and legitimate administration functions may provide continued access without deploying a large custom toolset.
NetworkCWE-613Public exploit reference
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-57815Official EUVD mapping

File Browser versions from 2.50.0 through 2.63.21 fail to validate JWT expiration when proxy authentication is configured with a non-default logout page. Attackers with a previously valid token can access protected routes and administrative endpoints indefinitely, and exchange expired tokens for fresh ones via the renewal endpoint.

Official EUVD record ↗
Cyber Security Agency of Singapore · English · CSA-SB-20260819Security Bulletin 19 Aug 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 19 Aug 2026, published on 19 August 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CSIRT Italia · Italian · file-browser-disponibili-poc-per-lo-sfruttamento-di-nuove-vulnerabilitaFile Browser: disponibili PoC per lo sfruttamento di nuove vulnerabilità

Nel dettaglio la vulnerabilità identificata tramite la CVE-2026-73613, di tipo "Improper Link Resolution", con score CVSS 3.1 pari a 8.2, interessa il meccanismo di gestione della cache TUS di File Browser. Tale vulnerabilità è dovuta all'utilizzo di operazioni di cancellazione effettuate su percorsi filesystem che possono essere modificati tramite collegamenti simbolici ( symlink ) durante una specifica finestra temporale. Un utente malintenzionato autenticato potrebbe sfruttare la vulnerabilità per eludere meccanismi di sicurezza e indurre il sistema a eliminare file arbitrari sul filesystem dei sistemi interessati. La seconda vulnerabilità, identificata tramite la CVE-2026-73612, di tipo "Authorization Bypass" e con score CVSS 4.0 pari a 8.6, è causata da meccanismi di controllo non adeguati sugli elementi discendenti durante le operazioni ricorsive di copia, rinomina ed eliminazione. Nel dettaglio, i controlli di autorizzazione vengono applicati esclusivamente alla directory oggetto dell'operazione, senza considerare le eventuali restrizioni associate ai file e alle sottodirectory in essa contenuti. Un utente autenticato malintenzionato potrebbe quindi copiare o rinominare una directory per accedere a file e cartelle discendenti normalmente soggetti a restrizioni di accesso, oppure eliminare la directory padre determinando la cancellazione dei relativi contenuti. La terza vulnerabilità, identificata tramite la CVE-2026-73611, di tipo "Insufficient Session Expiration" e con score CVSS 4.0 pari a 7.6, riguarda il meccanismo di autenticazione proxy basato su token JWT di File Browser. Tale vulnerabilità è dovuta alla mancata verifica della scadenza dei token in specifiche configurazioni che prevedono l'utilizzo di una pagina di logout non di default. Nel dettaglio, il sistema può continuare a considerare validi token ormai scaduti e consentirne il rinnovo tramite gli appositi endpoint di autenticazione. Un attaccante in possesso di un token precedentemente valido potrebbe quindi mantenere l'accesso a funzionalità protette e risorse amministrative oltre il periodo previsto, eludendo i meccanismi di autenticazione.

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
filebrowser: 2.50.0 ≤ 2.63.21
Fixed
An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 13 Aug 2026 · Last source change 30 Sept 2026, 17:20 UTC · CWE-613 · Insufficient Session Expiration

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-57815
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD not scheduled

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Vendor guidanceAuthoritative vendor guidance changed: removed remediation: acn.gov.it/file-browser-disponibili-poc-per-lo-sfruttamento-di-nuove-vulnerabilita.
    Before
    remediation: acn.gov.it/file-browser-disponibili-poc-per-lo-sfruttamento-di-nuove-vulnerabilita
    After
    no authoritative guidance recorded
    CNA ↗
  2. Remediation statusRemediation status changed from Mitigation available to Awaiting fix.
    Before
    Mitigation available
    After
    Awaiting fix
    CNA ↗
  3. Vendor guidanceAuthoritative vendor guidance changed: removed remediation: github.com/GHSA-v3jv-rmh2-635j.
    Before
    remediation: github.com/GHSA-v3jv-rmh2-635j
    After
    no authoritative guidance recorded
    CNA ↗
  4. Affected versionsThe structured affected or fixed version information changed.
    Before
    See the vendor and CVE records for the affected range. · Fixed: < 2.50.0
    After
    filebrowser: 2.50.0 ≤ 2.63.21 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
  5. Remediation statusRemediation status changed from Patch available to Awaiting fix.
    Before
    Patch available
    After
    Awaiting fix
    CNA ↗
  6. Public exploit evidencePublic exploit evidence changed from No public exploit to Public exploit reference.
    Before
    No public exploit
    After
    Public exploit reference
    CVE.org ↗
  7. Remediation statusRemediation status changed from Awaiting fix to Mitigation available.
    Before
    Awaiting fix
    After
    Mitigation available
    CSIRT Italia ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Remediation guidance recorded
ENISA EUVD · EUVD-2026-57815↗CSIRT Italia remediation guidance↗CISA Vulnrichment SSVC evidence↗CVE authority or vendor reference · GitHub GHSA-V3JV-RMH2-635J↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-73611 · cve.blacktree.nl