CVE-2026-42261Public exploitNetwork attack vector

Authenticated SSRF via noncanonical IPv6 address parsing

Published May 8, 2026 · Updated May 8, 2026

SSRF in PromptHub 0.4.9 through 0.5.3 allows remote authenticated users to read trusted HTTPS resources via crafted IPv6 URLs. The isPrivateIPv6 check in apps/web/src/utils/remote-http.ts compares or partially parses textual IPv6 forms instead of canonicalizing them, so mapped or expanded addresses reach loopback and private IPv4 targets. Any user or admin account can invoke the endpoint; response bodies up to 5 MB are exposed, but stock deployments can reach only HTTPS targets trusted by the PromptHub process.

CVSS severity7.1
High
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SSRF in PromptHub 0.4.9 through 0.5.3 allows remote authenticated users to read trusted HTTPS resources via crafted IPv6 URLs. The isPrivateIPv6 check in apps/web/src/utils/remote-http.ts compares or partially parses textual IPv6 forms instead of canonicalizing them, so mapped or expanded addresses reach loopback and private IPv4 targets. Any user or admin account can invoke the endpoint; response bodies up to 5 MB are exposed, but stock deployments can reach only HTTPS targets trusted by the PromptHub process.

The record

CVE
CVE-2026-42261
Published
May 8, 2026
Updated
May 8, 2026
Vendor
legeling
Product
PromptHub
Classifications
CWE-693, CWE-918, CWE-20, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 8, 2026CVE publishedPublication date reported by the CVE source.
  2. May 8, 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=>= 0.4.9, < 0.5.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

legeling · PromptHubversion=>= 0.4.9, < 0.5.4

Published CVSS scores

7.1GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-693Protection Mechanism Failure
CWE-918Server-Side Request Forgery (SSRF)
CWE-20Improper Input Validation
T1190Exploit Public-Facing Application

Public exploit references

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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