VulnerabilityPublished 13 Aug 2026Updated 31 Oct 2026

CVE-2026-67338: JupyterLab · Stored XSS in extension manager through package metadata unsanitized URI protocol

Affects jupyterlabSource GCVE Database

Compare

Not known to be exploited · CVSS 5.1 Medium : upgrade to 4.5.9 when convenient.

Data as of 31 Oct 2026, 17:05 UTC

CVSS 4.0 base score

5.1Medium

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 4.5.9

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: Active
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: None
Subsequent system confidentiality: Low
Subsequent system integrity: Low
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Active: Successful exploitation of this vulnerability requires a targeted user to perform specific, conscious interactions with the vulnerable system and the attacker’s payload, or the user’s interactions would actively subvert protection mechanisms which would lead to exploitation of the vulnerability.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Subsequent System.
Subsequent system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Subsequent System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade jupyterlab to 4.5.9.

Affected software

Product	Affected	Fixed in
Homebrewjupyterlab`pkg:brew/jupyterlab`Other threats	Affected >=1.2.0 <4.5.9	Fixed in 4.5.9

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

AI-suggested

This vulnerability is patched in JupyterLab version 4.5.9. Users and administrators should upgrade to version 4.5.9 or later to remediate this issue. No other mitigation is required if the patch is applied.

Description

JupyterLab versions from 1.2.0 up to but not including 4.5.9 contain a stored cross-site scripting (XSS) vulnerability in the Extension Manager. A malicious PyPI package can include a 'javascript:' URL in its metadata, which JupyterLab renders as a clickable homepage link without validating the URL protocol. When a user clicks this link, attacker-controlled JavaScript executes in the JupyterLab origin. This vulnerability requires the Extension Manager to be enabled with the default PyPI source and the malicious package to appear in the user's extension list.

Impact

An attacker who publishes a malicious package to PyPI can cause arbitrary JavaScript execution in the context of the JupyterLab origin when a user clicks the extension's homepage link in the Extension Manager. This can lead to potential compromise of user sessions or data within JupyterLab. The attack requires user interaction (clicking the link) and the Extension Manager to be enabled with the default PyPI source. There is no indication of privilege escalation or remote code execution beyond the XSS impact.

Summary

CVE-2026-67338 is a stored XSS vulnerability in JupyterLab's Extension Manager caused by unsanitized URI protocols in package metadata URLs. Specifically, a malicious PyPI package can specify a 'javascript:' URL in its [project.urls] metadata fields. JupyterLab's frontend renders this URL as the extension's homepage link without validating or sanitizing the protocol, allowing execution of arbitrary JavaScript when a user clicks the extension name. The vulnerability affects versions >=1.2.0 and <4.5.9. It was patched in version 4.5.9 with commits 4e61e07 and d5d961f. No exploitation in the wild is currently known.

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 31 Oct 2026, 17:05 UTC

Technical details

References

Community reviews

Related threats