Summary
baserCMS unsafely deserializes widget-area data, allowing a crafted serialized object graph to trigger command execution as the web-server user. Exploitation generally requires administrator-level widget-write access or equivalent access obtained through another vulnerability, after which ordinary page requests may repeatedly trigger the stored payload.
baserCMS unsafely deserializes widget-area data, allowing a crafted serialized object graph to trigger command execution as the web-server user. Exploitation generally requires administrator-level widget-write access or equivalent access obtained through another vulnerability, after which ordinary page requests may repeatedly trigger the stored payload.
Affected context
The issue occurs in baserCMS widget-area handling when a submitted non-array value can be stored without normal serialization and is later passed to unserialize() without restricting permitted classes. This affects deployments where an attacker can cause crafted widget data to be stored through the administrative JSON API, including cases where write capability is obtained by chaining another vulnerability.
The issue occurs in baserCMS widget-area handling when a submitted non-array value can be stored without normal serialization and is later passed to unserialize() without restricting permitted classes. This affects deployments where an attacker can cause crafted widget data to be stored through the administrative JSON API, including cases where write capability is obtained by chaining another vulnerability.
Exploit preconditions
- Attack surface: Administrative widget-management functionality and subsequent entity-read paths
- Required access: Administrator privileges or equivalent widget-write capability; unauthenticated access alone does not initially plant the payload
- Trigger point: Deserialization during front-end rendering, API responses, or other widget-entity reads
- Why exploitation is possible: Stored data is deserialized without an allowed-classes restriction, allowing object graphs to invoke available process-execution gadget chains
- Persistence condition: The database value may trigger repeatedly until the affected row is repaired or removed
- Attack surface: Administrative widget-management functionality and subsequent entity-read paths
- Required access: Administrator privileges or equivalent widget-write capability; unauthenticated access alone does not initially plant the payload
- Trigger point: Deserialization during front-end rendering, API responses, or other widget-entity reads
- Why exploitation is possible: Stored data is deserialized without an allowed-classes restriction, allowing object graphs to invoke available process-execution gadget chains
- Persistence condition: The database value may trigger repeatedly until the affected row is repaired or removed
Why this happens
The vulnerability results from treating attacker-influenced widget data as trusted serialized PHP state. When a non-array submission bypasses normal serialization handling, the value can be stored unchanged and later processed by unserialize() without class restrictions.
This maps to CWE-502: Deserialization of Untrusted Data. The insecure pattern permits unexpected object construction and magic-method or gadget-chain behavior during entity reads, bypassing protections that would otherwise be applied during ordinary object construction.
The vulnerability results from treating attacker-influenced widget data as trusted serialized PHP state. When a non-array submission bypasses normal serialization handling, the value can be stored unchanged and later processed by unserialize() without class restrictions.
This maps to CWE-502: Deserialization of Untrusted Data. The insecure pattern permits unexpected object construction and magic-method or gadget-chain behavior during entity reads, bypassing protections that would otherwise be applied during ordinary object construction.
Potential impact
- Arbitrary operating-system commands could execute as the web-server user
- The baserCMS application and its stored content may be compromised
- Persistent payloads may execute repeatedly on affected requests
- Sensitive application data could be accessed or modified
- The server could be used for lateral movement or further compromise
- Arbitrary operating-system commands could execute as the web-server user
- The baserCMS application and its stored content may be compromised
- Persistent payloads may execute repeatedly on affected requests
- Sensitive application data could be accessed or modified
- The server could be used for lateral movement or further compromise
General mitigation guidance
Mitigation focuses on eliminating unsafe deserialization and reducing trust in widget data.
Common defensive patterns include:
- Use structured, safe formats for widget state instead of native PHP serialization
- Reject unexpected scalar values and enforce strict schemas before persistence
- If legacy serialization is unavoidable, apply an explicit allowed-classes policy and validate the resulting data type
- Keep widget-write capabilities narrowly scoped and protected by strong authorization controls
- Minimize web-server privileges and restrict process-spawning capabilities where practical
- Treat data written through administrative APIs as untrusted until validated and normalized
- Repair or remove previously stored values that do not conform to the approved widget schema
Mitigation focuses on eliminating unsafe deserialization and reducing trust in widget data.
Common defensive patterns include:
- Use structured, safe formats for widget state instead of native PHP serialization
- Reject unexpected scalar values and enforce strict schemas before persistence
- If legacy serialization is unavoidable, apply an explicit allowed-classes policy and validate the resulting data type
- Keep widget-write capabilities narrowly scoped and protected by strong authorization controls
- Minimize web-server privileges and restrict process-spawning capabilities where practical
- Treat data written through administrative APIs as untrusted until validated and normalized
- Repair or remove previously stored values that do not conform to the approved widget schema
How teams detect issues like this
Organizations can look for this issue through:
- Static analysis rules identifying unserialize() calls on request-derived or database-derived values
- Code review checks for missing allowed_classes restrictions and unsafe type coercion
- Tests confirming that widget APIs reject unexpected scalar or serialized-object input
- Database searches for anomalous serialized object markers or base64-encoded serialized values in widget fields
- Runtime monitoring for unexpected child-process creation by the web server
- Policy enforcement that prohibits native object deserialization for content-management data
Automated security scanning and code-review tools may help identify unsafe deserialization paths, but findings should be confirmed against actual data flows and authorization boundaries.
Organizations can look for this issue through:
- Static analysis rules identifying unserialize() calls on request-derived or database-derived values
- Code review checks for missing allowed_classes restrictions and unsafe type coercion
- Tests confirming that widget APIs reject unexpected scalar or serialized-object input
- Database searches for anomalous serialized object markers or base64-encoded serialized values in widget fields
- Runtime monitoring for unexpected child-process creation by the web server
- Policy enforcement that prohibits native object deserialization for content-management data
Automated security scanning and code-review tools may help identify unsafe deserialization paths, but findings should be confirmed against actual data flows and authorization boundaries.
