CVE-2017-9225: Oniguruma Project Oniguruma

Critical severity, CVSS 9.8. EPSS: 3.1% chance of exploitation in the next 30 days.

An issue was discovered in Oniguruma 6.2.0, as used in Oniguruma-mod in Ruby through 2.4.1 and mbstring in PHP through 7.1.5. A stack out-of-bounds write in onigenc_unicode_get_case_fold_codes_by_str() occurs during regular expression compilation. Code point 0xFFFFFFFF is not properly handled in unicode_unfold_key(). A malformed regular expression could result in 4 bytes being written off the end of a stack buffer of expand_case_fold_string() during the call to onigenc_unicode_get_case_fold_codes_by_str(), a typical stack buffer overflow.

Affected products

• Oniguruma Project Oniguruma: version 6.2.0 only
• PHP PHP: up to and including 7.1.5
• Ruby-Lang Ruby: up to and including 2.4.1

Published 2017-05-24. Last modified 2026-06-17.