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CVE-2026-48901 Joomla! Project CVE debrief

CVE-2026-48901 describes a vulnerability in the `InputFilter::getInstance()` method where a security-sensitive parameter was omitted from the instance cache key construction. This flaw could allow improper cache reuse across different security contexts, potentially leading to security boundary violations in input filtering operations. The vulnerability was published on 2026-05-26 and is currently undergoing analysis in the NVD. The affected product is Joomla, based on the security advisory reference from the Joomla Security Centre. No CVSS score or severity rating has been assigned at this time. The issue has not been added to CISA's Known Exploited Vulnerabilities catalog.

Vendor
Joomla! Project
Product
Joomla! CMS
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-26
Original CVE updated
2026-05-28
Advisory published
2026-05-26
Advisory updated
2026-05-28

Who should care

Joomla site administrators, particularly those running multi-site installations or shared hosting environments; security teams managing Joomla-based web applications; developers of Joomla extensions that rely on custom InputFilter configurations

Technical summary

The `InputFilter::getInstance()` method in Joomla constructs a cache key to reuse InputFilter instances. A security-sensitive parameter was inadvertently excluded from this cache key calculation, meaning that instances created with different security parameters could be incorrectly reused from cache. This could result in input filtering being applied with incorrect security rules—potentially allowing more permissive filtering than intended, or conversely blocking legitimate input. The vulnerability affects the integrity of security context separation in Joomla's input sanitization layer.

Defensive priority

medium

Recommended defensive actions

  • Review Joomla security advisory 20260517 for detailed technical information and affected versions
  • Apply security updates from Joomla when available, prioritizing systems with multi-tenant or shared hosting configurations where InputFilter context separation is critical
  • Audit custom extensions or integrations that directly invoke InputFilter::getInstance() with custom security parameters
  • Monitor NVD entry for CVSS scoring and updated analysis once completed
  • Review application logs for unexpected InputFilter behavior or cache-related anomalies

Evidence notes

The vulnerability description indicates incorrect cache key construction in `InputFilter::getInstance()`, which is a core Joomla security component. The reference to developer.joomla.org/security-centre/1049-20260517-core-incorrect-cache-key-construction-for-inputfilter-objects.html confirms this is a Joomla core issue. The NVD status shows 'Undergoing Analysis' as of the last modification timestamp.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-48901 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-48901

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-48901 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-48901

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source reference

    Unverified legacy reference

    URL: https://developer.joomla.org/security-centre/1049-20260517-core-incorrect-cache-key-construction-for-inputfilter-objects.html

    [email protected]

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.