Quick answers
- Is CVE-2026-120635 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-120635 being exploited in the wild.
- How severe is CVE-2026-120635?
- Informational severity, published 4 November 2026.
- Which products and versions are affected?
- Perl CGI before 5.00.
- Is there a fix for CVE-2026-120635?
- Yes: fixed in CGI 5.00. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-120635 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-120635?
- Check whether you run Perl CGI 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: CGI 5.00
Technical details
The CGI module's multipart/form-data parser contains multiple RFC 2046 deviations: it matches boundaries anywhere in the buffer rather than only at the start of a line, uses the boundary without its leading "--" for certain User-Agent values, extracts Content-Disposition headers from within quoted parameter values, and corrupts parts when boundaries occur near the 4096-byte read buffer boundary. These parsing discrepancies allow an attacker to craft form data that parses one way by the CGI module and differently by RFC-compliant proxies or WAFs, enabling field smuggling. An unauthenticated attacker on the network can exploit this with a crafted POST request; no user interaction is required.
Affected products
- Perl CGI before 5.00
Timeline
- 2026-11-04: disclosed