CVE-2026-39843Public exploitNetwork attack vector

Authenticated internal data read via favicon redirects

Published Apr 9, 2026 · Updated Apr 9, 2026

SSRF in Plane allows remote authenticated users to read internal network resources through a crafted Add link request. The fetch_and_encode_favicon() function passes a link-derived favicon URL to requests.get() with automatic redirects enabled but does not revalidate each redirect destination. Low-privileged access is sufficient; a public HTML page can redirect the favicon request to a private address and expose its response as base64 data.

CVSS severity7.7
High
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SSRF in Plane allows remote authenticated users to read internal network resources through a crafted Add link request. The fetch_and_encode_favicon() function passes a link-derived favicon URL to requests.get() with automatic redirects enabled but does not revalidate each redirect destination. Low-privileged access is sufficient; a public HTML page can redirect the favicon request to a private address and expose its response as base64 data.

The record

CVE
CVE-2026-39843
Published
Apr 9, 2026
Updated
Apr 9, 2026
Vendor
Plane
Product
Plane
Classifications
CWE-918
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 9, 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=>= 0.28.0, < 1.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Plane · Planeversion=>= 0.28.0, < 1.3.0

Published CVSS scores

7.7GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/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-918Server-Side Request Forgery (SSRF)

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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