HTTP response splitting in Dancer2
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA.
Summary
Dancer2 versions before 2.2.0 for Perl do not strip CR and LF from response header names in headers_to_array. The routine removes CR and LF from each header value but not from the name. A name carrying them therefore reaches the PSGI server intact. A server that does not validate keys writes it to the wire, so the bytes after the CRLF arrive as their own header line. The application has to derive the header name from request data, not just the value. An attacker who controls that data adds their own headers and splits the response.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | Dancer2 | before 2.2.0 | 2.2.0 | Patch available | CNA |
- Dancer2 Vendor— Affected before 2.2.0 Fixed in 2.2.0 Patch available CNA
Remediation
- Fix · CNA Dancer2 Fixed in 2.2.0
Timeline
- 2026-10-02 Threatist record created from CVE-2026-93711
- 2026-10-03 Alias added: GHSA-vp8p-vxw7-c877
References
Sources
- CVE-2026-93711 · CVE Program
- CVE-2026-93711 · NVD
- FIRST EPSS
- GHSA-vp8p-vxw7-c877 · GitHub Advisory Database · CC BY 4.0
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