Security readout for executives and security teams
Plain-English summary
Rucio WebUI can store unsafe RSE metadata and later show it to users without proper encoding. If a privileged attacker can modify that metadata, JavaScript may run in another user’s browser when they view affected pages. The main business risk is account/session compromise or unauthorized actions inside Rucio, not server takeover.
Executive priority
Prioritize within the normal vulnerability remediation cycle, faster for internet-facing or multi-user Rucio portals. This is not marked as known exploited, but stored XSS can undermine trust in administrative workflows and user sessions.
Technical view
CVE-2026-25734 is a stored XSS in Rucio WebUI RSE metadata. Affected versions are before 35.8.3, 36.0.0rc1 through before 38.5.4, and 39.0.0rc1 through before 39.3.1. CVSS 3.1 is 6.1: network exploitable, low complexity, high privileges required, user interaction required, with high confidentiality and integrity impact.
Likely exposure
Exposure is limited to organizations running Rucio WebUI on affected versions, especially where users can edit RSE metadata. Internet exposure increases risk, but the source indicates high privileges are required to plant the stored content.
Exploitation context
No provided source or KEV status indicates active exploitation. Successful abuse requires an attacker with sufficient privileges to persist malicious metadata and a victim user to view the affected WebUI page.
Researcher notes
The advisory attributes the issue to persisted attacker-controlled input rendered without proper output encoding in RSE metadata. CWE mappings include CWE-79 and CWE-1004. Evidence provided identifies fixed releases but does not include exploit-in-the-wild claims or detailed workaround instructions beyond upgrading and XSS-safe handling.
Mitigation direction
- Upgrade Rucio to 35.8.3, 38.5.4, or 39.3.1 as applicable.
- Review vendor advisory GHSA-h9fp-p2p9-873q for deployment-specific guidance.
- Apply standard XSS defenses: context-aware output encoding and safe handling of untrusted metadata.
- Restrict RSE metadata modification rights to trusted administrators until upgraded.
Validation and detection
- Inventory Rucio WebUI deployments and confirm exact installed versions.
- Check whether versions fall in the affected ranges listed by the advisory.
- Confirm upgrade to a fixed release in test and production environments.
- Review RSE metadata permissions and recent changes for unexpected entries.
- Validate WebUI rendering follows vendor fix behavior without using offensive payloads.
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-1004: 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 lookupCWE-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. 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 lookupCVE-2026-25734 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
- 6.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:H/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:H/UI:R/S:U/C:H/I:H/A:N0.95.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.1MediumVector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/rucio/rucio/security/advisories/GHSA-h9fp-p2p9-873qCVE reference · x_refsource_CONFIRM
- https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.htmlCVE 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.
Sensitive Cookie Without 'HttpOnly' Flag
Sensitive Cookie Without 'HttpOnly' Flag represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.