Security readout for executives and security teams
Plain-English summary
Unauthenticated visitors could make Craft CMS write attacker-chosen content into predictable server-side PHP session files. By itself, this is not described as full remote code execution, but the source says that content could be accessed and executed through a separate vulnerability. CISA KEV inclusion means exploitation has been observed and should raise urgency.
Executive priority
Treat this as high priority despite medium CVSS because CISA KEV indicates real-world exploitation. Patch exposed Craft CMS assets promptly and look for evidence of chained activity.
Technical view
Craft CMS redirected unauthenticated requests to login and created session files under /var/lib/php/sessions using a client-visible session value. It stored the requested return URL without sanitizing parameters, allowing arbitrary values in a known local file. Craft CMS 4.15.3 and 5.7.5 address the issue.
Likely exposure
Internet-facing Craft CMS deployments that have not updated to 4.15.3 or 5.7.5 are the primary concern. Exposure is higher where PHP session files are reachable through another local-file or execution flaw.
Exploitation context
The source bundle marks this CVE as in CISA KEV, supporting active exploitation. The described issue is most dangerous as part of a chain: it plants attacker-controlled content in a known session file that another flaw may access or execute.
Researcher notes
Evidence supports arbitrary session-file content injection, not a standalone exploit path. Do not assume code execution without an independent file access or execution vulnerability. The source bundle does not provide detailed indicators, exploit mechanics, or non-upgrade mitigations.
Mitigation direction
- Upgrade Craft CMS to 5.7.5 or 4.15.3, as applicable.
- Review Craft CMS release notes and vendor guidance for any branch-specific instructions.
- Prioritize internet-facing Craft CMS instances because KEV status indicates exploitation.
- Investigate suspicious PHP session files containing unexpected return URL data or code-like content.
Validation and detection
- Inventory Craft CMS versions across production, staging, and externally hosted environments.
- Confirm deployed versions are 5.7.5, 4.15.3, or later patched releases.
- Check whether PHP session storage uses /var/lib/php/sessions or another local path.
- Review web and application logs for unusual unauthenticated requests to authenticated routes.
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-472: 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-2025-35939 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
- 6.9 (4.0)
- Known Exploited
- Yes
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA: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.
CISA KEV status
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:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
6.9MediumVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Source materials
- CVE List V5 sourceCVE List V5
- urlCVE reference
- urlCVE reference
- urlCVE reference
- urlCVE reference
- urlCVE reference
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-35939CVE reference · government-resource
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.
External Control of Assumed-Immutable Web Parameter
External Control of Assumed-Immutable Web Parameter represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.