Security readout for executives and security teams
Plain-English summary
CVE-2026-25138 lets unauthenticated users tell whether a Rucio WebUI username exists based on different login error messages. This does not directly compromise accounts, but it can help attackers build valid user lists for phishing, password guessing, or credential-stuffing campaigns.
Executive priority
Treat as a planned security update, higher priority for public-facing Rucio WebUI systems. The flaw is not a direct takeover bug, but it lowers attacker effort for targeted credential attacks against scientific data environments.
Technical view
Rucio WebUI versions before 35.8.3, 38.5.4, and 39.3.1 expose a username enumeration weakness at the login endpoint. The issue is CWE-204: observable response discrepancy. CVSS is 5.3, network exploitable, low attack complexity, no privileges or user interaction required, with low confidentiality impact.
Likely exposure
Exposure is limited to organizations running affected Rucio WebUI versions with the login endpoint reachable by untrusted users. Internet-facing or broadly accessible scientific data portals have higher practical risk than restricted internal deployments.
Exploitation context
The advisory describes unauthenticated username enumeration through differing login errors. CISA KEV status is false in the provided data, and no cited source states active exploitation. The main concern is attacker reconnaissance that enables later account-focused attacks.
Researcher notes
Focus validation on version identification and login error consistency. Avoid user enumeration testing against production accounts without authorization. Sources name fixed releases but do not provide evidence of exploitation in the wild.
Mitigation direction
- Upgrade Rucio to 35.8.3, 38.5.4, or 39.3.1 as appropriate.
- Review vendor advisory GHSA-38wq-6q2w-hcf9 for deployment-specific guidance.
- Restrict WebUI login exposure where operationally feasible.
- Follow OWASP guidance: use generic authentication error messages.
Validation and detection
- Inventory Rucio WebUI deployments and record running versions.
- Confirm affected ranges: below 35.8.3, 38.5.4, or 39.3.1.
- Verify the WebUI login endpoint is not publicly exposed unnecessarily.
- After upgrade, confirm login failures use consistent generic messages.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-204: 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 lookupCVE-2026-25138 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/rucio/rucio/security/advisories/GHSA-38wq-6q2w-hcf9CVE reference · x_refsource_CONFIRM
- https://cheatsheetseries.owasp.org/cheatsheets/Authentication_Cheat_Sheet.html#authentication-and-error-messagesCVE reference · x_refsource_MISC
- https://github.com/rucio/rucio/releases/tag/35.8.3CVE reference · x_refsource_MISC
- https://github.com/rucio/rucio/releases/tag/38.5.4CVE reference · x_refsource_MISC
- https://github.com/rucio/rucio/releases/tag/39.3.1CVE 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 Response Discrepancy
Observable Response Discrepancy represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.