CVE-2026-40470Network attack vector

Session hijacking via same-origin uploaded content

Published Apr 23, 2026 · Updated Apr 23, 2026

Stored XSS in Haskell.org hackage-server before 0.6 allows remote authenticated users to hijack privileged browser sessions. Package source browsing and documentation endpoints serve maintainer-supplied HTML, JavaScript, and quick-jump assets as active same-origin content without isolation. A malicious package maintainer must cause a user with latent credentials to browse the content; injected script can perform any repository action available to that user.

CVSS severity9.9
Critical
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Haskell.org hackage-server before 0.6 allows remote authenticated users to hijack privileged browser sessions. Package source browsing and documentation endpoints serve maintainer-supplied HTML, JavaScript, and quick-jump assets as active same-origin content without isolation. A malicious package maintainer must cause a user with latent credentials to browse the content; injected script can perform any repository action available to that user.

The record

CVE
CVE-2026-40470
Published
Apr 23, 2026
Updated
Apr 23, 2026
Vendor
Haskell.org
Product
hackage-server
Classifications
CWE-79, T1189
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.1 <0.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Haskell.org · hackage-serverversion=0.1 <0.6

Published CVSS scores

9.9redhat-cnalrCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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