CVE-2026-87015Public exploitNetwork attack vector

Account takeover via cross-server session cookie leakage

Published Sep 9, 2026 · Updated Sep 10, 2026

Sensitive information exposure in Open WebUI 0.6.27 through 0.11.0 allows attackers to take over accounts via leaked session cookies. The tool-loading routine in backend/open_webui/utils/tools.py closes over a shared cookie jar instead of binding each jar to its external-tool callable, causing a bearer-authenticated request to receive cookies from the connection processed last. Exploitation requires multiple attached tool servers, a session or system OAuth connection processed last, and a user tool call reaching a server operated by the attacker.

CVSS severity6.8
Medium
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Sensitive information exposure in Open WebUI 0.6.27 through 0.11.0 allows attackers to take over accounts via leaked session cookies. The tool-loading routine in backend/open_webui/utils/tools.py closes over a shared cookie jar instead of binding each jar to its external-tool callable, causing a bearer-authenticated request to receive cookies from the connection processed last. Exploitation requires multiple attached tool servers, a session or system OAuth connection processed last, and a user tool call reaching a server operated by the attacker.

The record

CVE
CVE-2026-87015
Published
Sep 9, 2026
Updated
Sep 10, 2026
Vendor
Open WebUI
Product
Open WebUI
Classifications
CWE-201, T1539
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 10, 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=>= 0.6.27, < 0.11.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Open WebUI · Open WebUIversion=>= 0.6.27, < 0.11.1

Published CVSS scores

6.8GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-201Insertion of Sensitive Information Into Sent Data
T1539Steal Web Session Cookie

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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