VulnerabilityPublished 13 Aug 2026Updated 29 Oct 2026

CVE-2026-59927: Mistune directives/include · mutual `

Affects jupyterlabSource GCVE Database

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Authoritative record:CVE-2026-59927· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium : upgrade to 4.6.1 when convenient.

Data as of 30 Oct 2026, 09:02 UTC

CVSS 3.1 base score

5.3Medium

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

Patch: Available – fixed in 4.6.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: Low

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 8 Jul 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 29 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 4.6.1.

Affected software

Product	Affected	Fixed in
Homebrewjupyterlab`pkg:brew/jupyterlab`Other threats	Affected >=1.2.0 <4.6.1	Fixed in 4.6.1

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

AI-suggested

A patch is available in mistune version 4.6.1 that fixes the vulnerability by adding detection of indirect include cycles to prevent infinite recursion. Users should upgrade to version 4.6.1 or later. Until patched, applications should consider restricting user ability to upload or include arbitrary markdown files or implement application-level checks to prevent mutual includes. The vendor advisory confirms the fix is available and recommends upgrading.

Description

CVE-2026-59927 is a vulnerability in the mistune Markdown renderer's Include directive that allows uncontrolled recursion via mutual includes of markdown files. The directive only detects direct self-inclusion but fails to detect indirect cycles where two or more files include each other. This leads to unbounded recursion until Python's recursion limit is exceeded, causing a RecursionError that crashes the rendering process. This can be exploited by an attacker who can upload or control markdown files to cause denial of service by crashing the renderer. The issue affects mistune versions used in jupyterlab from 1.2.0 up to but not including 4.6.1. A fix is available in version 4.6.1 that adds cycle detection to prevent infinite recursion.

Impact

An attacker with the ability to supply or upload markdown files to an application using mistune with the Include directive enabled can cause a denial of service by triggering infinite recursion. This results in a RecursionError that crashes the markdown rendering process and potentially the entire application request or job that invoked it. The impact is limited to denial of service (availability) with no confidentiality or integrity loss reported. The vulnerability requires the application to render user-supplied markdown files that can include other user-uploaded files.

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Affected software

Description

AI analysisMachine-generated, updated 30 Oct 2026, 09:02 UTC

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