Assessment
Why it matters
EPSS is 0.2%; technical severity is CVSS 2.1.
In PHP versions 8.2.* before 8.2.31, 8.3.* before 8.3.31, 8.4.* before 8.4.21, and 8.5.* before 8.5.6, a mismatch between encoding lists in Oniguruma and mbfl leads to a NULL pointer dereference, resulting in a segmentation fault and denial of service. The vulnerability is exploitable when user-controlled input can influence the encoding passed to mb_regex_encoding().
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.
- Vendor advisory from github.com
- 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:H/AT:P/PR:N/UI:A/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:X/U:Amber
- CWE
- CWE-476
- Affected versions
- PHP PHP (Start Including 8.2.0, End Excluding 8.2.31 | Start Including 8.3.0, End Excluding 8.3.31 | 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 8.2.31, 8.3.31, 8.4.21, 8.5.6)
- Published
- 10 May 2026
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Active
Signal timeline
- CVE published
- Latest EPSS score: 0.2%
- Signal calculated at 6