Quick answers
- Is CVE-2026-104259 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-104259 being exploited in the wild.
- How severe is CVE-2026-104259?
- Medium severity, with a CVSS score of 5.4, published 9 November 2026.
- Which products and versions are affected?
- OWASP Modsecurity 2.x before 2.9.15, 3.0.x before 3.0.17.
- Is there a fix for CVE-2026-104259?
- Yes: fixed in ModSecurity 2.9.15, 3.0.17. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-104259 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-104259?
- Check whether you run OWASP Modsecurity at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: ModSecurity 2.9.15, 3.0.17
Technical details
The t:removeComments transformation in ModSecurity 2.9.x and 3.0.x contains a logic error where it copies the character immediately after a comment terminator without re-evaluating whether that character is part of a new comment. This allows adjacent comments to remain in the transformed output, bypassing WAF rules that depend on comment stripping. Additionally, when a comment terminator is the final input, the code reads one byte beyond the buffer boundary.
Affected products
- OWASP ModSecurity 2.x before 2.9.15, 3.0.x before 3.0.17
Timeline
- 2026-11-09: disclosed