CVE-2026-35536
Tornadoweb Tornado ≤ 6.5.5
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:NSummary
CVE-2026-35536 is a high-severity Improper Handling of Invalid Use of Special Elements (CWE-159) vulnerability in Tornadoweb Tornado. Its CVSS base score is 7.2 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 15th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-35536 is a cookie attribute injection vulnerability affecting the Tornado Python web framework in versions prior to 6.5.5. The issue arises because the domain, path, and samesite arguments passed to the .RequestHandler.set_cookie method are not validated for crafted characters, allowing attackers to inject malicious content into cookie attributes. This flaw is rated with a CVSS v3.1 base score of 7.2 (AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N) and is associated with CWE-159 (Improper Handling of Invalid Use of Special Elements).
Remote attackers can exploit this vulnerability without authentication or user interaction over the network with low complexity. By supplying specially crafted inputs to the affected set_cookie arguments, they can manipulate cookie attributes such as domain, path, or samesite, potentially overriding intended cookie behaviors. Successful exploitation enables limited confidentiality and integrity impacts, such as unauthorized access to low-sensitivity data or minor modifications to application state, with a change in scope due to cross-context influence.
The Tornado project addressed this vulnerability in version 6.5.5, as detailed in the release notes at https://github.com/tornadoweb/tornado/releases/tag/v6.5.5 and the security advisory at https://github.com/tornadoweb/tornado/security/advisories/GHSA-78cv-mqj4-43f7. Security practitioners should upgrade to Tornado 6.5.5 or later to mitigate the issue, and review any custom cookie-handling code for similar validation gaps.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-18574
Vulnerability Data
In Tornado before 6.5.5, cookie attribute injection could occur because the domain, path, and samesite arguments to .RequestHandler.set_cookie were not checked for crafted characters.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
SI-10 requires validity checks on information inputs, directly stopping improper handling of special elements before they affect behavior or integrity.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly enforce input validation and special-element handling to prevent the weakness.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can discover the weakness but does not itself implement the preventive control.
Secure development lifecycle mandates input validation and sanitization that directly prevents improper handling of special elements.
Application security requirements explicitly call for controls against malformed or malicious input.
Secure architecture principles reduce attack surface but do not prescribe specific input-filtering techniques.
Secure coding standards require proper escaping, quoting and validation of special characters in user input.