Security readout for executives and security teams
Plain-English summary
File Browser versions before 2.55.0 can reveal whether a username exists by responding at different speeds during login. This does not grant access by itself, but it helps attackers build valid user lists for password attacks or targeted phishing.
Executive priority
Prioritize patching internet-facing File Browser systems. This is not a direct takeover flaw, but it weakens account security by helping attackers identify valid users.
Technical view
CVE-2026-23849 is a CWE-208 observable timing discrepancy in File Browser’s /api/login JSONAuth.Auth flow. Missing users return immediately, while existing users trigger bcrypt password verification, creating a measurable timing difference. It is unauthenticated, network-accessible, and affects filebrowser/filebrowser before 2.55.0. Version 2.55.0 patches the issue.
Likely exposure
Exposed File Browser deployments running versions earlier than 2.55.0 are the likely concern, especially internet-facing instances with reachable /api/login endpoints.
Exploitation context
The sources describe username enumeration via timing analysis. No provided source reports active exploitation, and the CVE is not marked KEV. Business risk is mainly attacker reconnaissance that can support credential attacks.
Researcher notes
The public record identifies the vulnerable logic and patch commit, but does not provide evidence of exploitation in the wild. Analysis should focus on version validation, endpoint exposure, and authentication telemetry rather than exploit reproduction.
Mitigation direction
- Upgrade File Browser to version 2.55.0 or later.
- Review the GitHub security advisory for vendor guidance.
- Reduce external exposure to File Browser login where operationally feasible.
- Monitor authentication logs for broad username guessing patterns.
Validation and detection
- Inventory File Browser instances and record deployed versions.
- Confirm whether any instance runs a version earlier than 2.55.0.
- Verify the /api/login endpoint is not unnecessarily internet-exposed.
- Review failed login telemetry for repeated username enumeration behavior.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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
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CWE-208: 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 lookupCredential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupDatabase behavior lookup
The CVE wording references database injection or access, so collection and exfiltration review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-23849 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
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.
CVSS vector scores
1 official scoreWe 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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.3MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/filebrowser/filebrowser/security/advisories/GHSA-43mm-m3h2-3prcCVE reference · x_refsource_CONFIRM
- https://github.com/filebrowser/filebrowser/commit/24781badd413ee20333aba5cce1919d676e01889CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Observable Timing Discrepancy
Observable Timing Discrepancy represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.