CVE-2026-40470 | BDVDB-2026-328639 Detail

Description#

A critical XSS vulnerability affected hackage-server and hackage.haskell.org. HTML and JavaScript files provided in source packages or via the documentation upload facility were served as-is on the main hackage.haskell.org domain. As a consequence, when a user with latent HTTP credentials browses to the package pages or documentation uploaded by a malicious package maintainer, their session can be hijacked to upload packages or documentation, amend maintainers or other package metadata, or perform any other action the user is authorised to do.

Impact#

Per CVSS v3.1: confidentiality impact high, integrity impact high, availability impact low. Attack vector: network.

Weaknesses#

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

References#

https://osv.dev/vulnerability/HSEC-2024-0004

Exploit#

No public exploit known

History#

Version 12026-04-23Record published in the CVE List.

Published

Published: 2026-04-23
Last modified: 2026-04-23

Vendor information

Vendor: Not stated
Product: Not stated

Score

9.9 Critical

EPSS

less than 1%, Very Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 23.9.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Cross-Site Scripting

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

Vulnerable
>= 0.1 and < 0.6
Fixed
0.6

Scoring System

CVSS v4.0

Not available

CVSS v3.1

9.9 Critical

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L

Metric breakdown
Attack Vector	Network
Attack Complexity	Low
Privileges Required	Low
User Interaction	None
Scope	Changed
Confidentiality	High
Integrity	High
Availability	Low

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).