Vulnerability · Published Oct 12, 2026 · Assigned by GitHub_M
CVE-2026-104774OWASP Coraza WAF: jsDecode Off-by-One in Octal Escape Handling Enables WAF Bypass
Medium 5.8
In plain English
A medium-severity security flaw in coraza from corazawaf. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 25% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/corazawaf/coraza | no fix listed | GO-2026-6696 |
| Go | github.com/corazawaf/coraza/v2 | no fix listed | GO-2026-6696 |
| Go | github.com/corazawaf/coraza/v3 | 3.8.0 | GHSA-pc5q-qfxp-ggqv |
| Go | github.com/corazawaf/coraza/v3 | 3.8.0 | GO-2026-6696 |
Affected products (as reported)
Weakness: CWE-172, CWE-193, CWE-693 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
References
- https://github.com/corazawaf/coraza/security/advisories/GHSA-pc5q-qfxp-ggqv x_refsource_CONFIRM
- https://github.com/corazawaf/coraza/commit/f9b7afdbcedce7ad814663eaee2e342578ea3bb2 x_refsource_MISC
- https://github.com/corazawaf/coraza/releases/tag/v3.8.0 x_refsource_MISC