Coraza: jsDecode Off-by-One in Octal Escape Handling Enables WAF Bypass

Why it is Yellow

• CVSS 5.8 medium
• On your watchlist: Go

Affected packages

References

• https://github.com/advisories/GHSA-pc5q-qfxp-ggqv
• https://github.com/corazawaf/coraza/security/advisories/GHSA-pc5q-qfxp-ggqv
• https://github.com/corazawaf/coraza/commit/f9b7afdbcedce7ad814663eaee2e342578ea3bb2
• https://github.com/corazawaf/coraza/releases/tag/v3.8.0
• https://github.com/advisories/GHSA-pc5q-qfxp-ggqv

Original description

OWASP Coraza WAF is a golang modsecurity compatible web application firewall library. From 3.0.0 until 3.8.0, the t:jsDecode transformation in internal/transformations/js_decode.go:64-70 includes the backslash in the octal buffer, causing ParseInt to fail and return a null byte. The flaw is triggered when a rule relies on t:jsDecode and the request contains JavaScript octal escape sequences. An unauthenticated attacker can encode attack syntax with JavaScript octal escapes so the backend decodes the intended bytes while Coraza rules using t:jsDecode inspect corrupted null-byte output. The mismatch can bypass WAF rules and expose the protected application to attacks such as cross-site scripting or SQL injection. This issue is fixed in version 3.8.0.