Assessment
Why it matters
EPSS is 0.4%; technical severity is CVSS 6.3.
In PHP versions 8.4.* before 8.4.21 and 8.5.* before 8.5.6, DOMNode::C14N() method may process the XML data incorrectly, causing a circular linked list in the data structure representing the XML document. This may cause subsequent processing of the XML document to enter infinite loop, causing denial of service in the processing application.
Who should care
- Teams operating PHP
- Vulnerability and exposure management teams
- Security operations teams monitoring exploitation activity
Response plan
What I would do
- Confirm whether PHP is present in the environment.
- Identify affected versions and establish whether vulnerable services are exposed or reachable.
- Red Hat Security advisory RHSA-2026:22649
- Review relevant security telemetry for evidence of attempted or successful exploitation.
- Document the remediation decision and track it to verified completion.
Treatment intelligence
Remediation intelligence
Vendor sources are listed before government and third-party guidance. Confirm product applicability and change prerequisites before deployment.
Verification noteAutomated link verification has not completed for this guidance yet.
Technical details
- CVSS vector
- CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:X/V:X/RE:M/U:Amber
- CWE
- CWE-404
- Affected versions
- PHP PHP (Start Including 8.4.0, End Excluding 8.4.21 | Start Including 8.5.0, End Excluding 8.5.6)
- Fixed versions
- PHP PHP (Fixed from 8.4.21, 8.5.6)
- Published
- 10 May 2026
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
Signal timeline
- CVE published
- Latest EPSS score: 0.4%
- Signal calculated at 11