CVE-2026-40472
Published: 23 April 2026
Summary
CVE-2026-40472 is a critical-severity Cross-site Scripting (CWE-79) vulnerability in Osv (inferred from references). Its CVSS base score is 9.9 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 21.8th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-15 (Information Output Filtering).
Deeper analysis
CVE-2026-40472 is a stored Cross-Site Scripting (XSS) vulnerability, classified under CWE-79, affecting hackage-server. In this issue, user-controlled metadata from .cabal files is rendered into HTML href attributes without proper sanitization, enabling attackers to inject malicious scripts. The vulnerability received a CVSS v3.1 base score of 9.9 (AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L) and was published on 2026-04-23.
The attack requires low privileges (PR:L), allowing a registered user with the ability to submit .cabal files—such as package uploaders—to inject XSS payloads into metadata fields. These payloads persist in the server and execute in the context of other users' browsers when viewing affected package details, with no user interaction needed (UI:N). Exploitation achieves high confidentiality and integrity impacts (C:H/I:H), low availability impact (A:L), and scope change (S:C), potentially enabling session hijacking, data theft, or further compromise across the application's security context.
Mitigation details are available in the referenced advisory at https://osv.dev/vulnerability/HSEC-2026-0004.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-25235
Vulnerability details
In hackage-server, user-controlled metadata from .cabal files are rendered into HTML href attributes without proper sanitization, enabling stored Cross-Site Scripting (XSS) attacks.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Stored XSS in public-facing hackage-server directly enables injection/execution of malicious JavaScript in victim browsers (T1059.007) and exploitation of the exposed web application (T1190).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Filters user-controlled metadata from .cabal files prior to rendering into HTML href attributes, directly preventing stored XSS payload execution in viewers' browsers.
Validates metadata inputs from .cabal files to detect and reject malicious scripts before they are stored and rendered.
Restricts the format, length, and type of .cabal metadata inputs to limit opportunities for injecting XSS payloads.