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VulnerabilityPublished

CVE-2026-40470: hackage-server · Cross-site Scripting

Affects hackage-serverSource CVE Database V5

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Not known to be exploited · CVSS 9.9 Critical : upgrade to 0.6 as a priority.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
9.9Critical
How severe the flaw is on the 0–10 CVSS scale.

Contested

Critical score, yet low EPSS after six months
EPSS
0.3% chance of exploitation in 30 days – higher than 23% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.6
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 23 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade hackage-server to 0.6.

Affected software

ProductAffectedFixed in
Hackagehackage-serverpkg:hackage/hackage-serverOther threatsAffected
  • =0.1
Fixed in–
Hackagehackage-serverpkg:hackage/hackage-serverOther threatsAffected
  • >=0.1 <0.6
Fixed in
  • 0.6

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, users and administrators should exercise caution when interacting with untrusted packages or documentation on hackage.haskell.org. Consider restricting access or monitoring for suspicious activity related to package uploads and metadata changes.

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.

References

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