VulnerabilityPublished 5 Aug 2026

CVE-2026-66881: livebook · Relative Path Traversal

Affects livebookSource CVE Database V5

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Not known to be exploited · CVSS 7.0 High : upgrade to 0.19.9 or 0.18.7 soon.

Data as of 3 Nov 2026, 10:58 UTC

CVSS 4.0 base score

7.0High

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

EPSS: 0.6% chance of exploitation in 30 days – higher than 49% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.19.9, 0.18.7, 0.19.9-cuda12 +1

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: Active
Vulnerable system confidentiality: None
Vulnerable system integrity: High
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
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: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system 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 Vulnerable System 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 Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable 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 5 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 3 Nov 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 livebook to 0.19.9 or 0.18.7; livebook to 0.19.9-cuda12, 0.19.9, 0.18.7-cuda12 or 0.18.7.

Affected software

Product	Affected	Fixed in
livebook-devlivebook	Affected >=0.19.0 <0.19.9	Fixed in 0.19.9
livebook-devlivebook	Affected >=0.11.0 <0.18.7	Fixed in 0.18.7
livebook-devlivebook	Affected >=0.19.0-cuda12 <0.19.9-cuda12	Fixed in 0.19.9-cuda12
livebook-devlivebook	Affected >=0.19.0 <0.19.9	Fixed in 0.19.9
livebook-devlivebook	Affected >=0.11.0-cuda12 <0.18.7-cuda12	Fixed in 0.18.7-cuda12
livebook-devlivebook	Affected >=0.11.0 <0.18.7	Fixed in 0.18.7

CPE configurations (1)

cpe:2.3:a:livebook-dev:livebook:*:*:*:*:*:*:*:*

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

AI-suggested

If you cannot patch yet, users should avoid opening notebooks from untrusted sources. Monitoring for updates from the livebook-dev project is recommended to apply any forthcoming patches that address this path traversal issue.

Description

CVE-2026-66881 is a relative path traversal vulnerability in livebook-dev's livebook software. It allows an attacker to craft a malicious notebook that writes files with attacker-controlled content to arbitrary paths on the victim's system. This occurs because the import process does not properly validate file entry names, enabling path traversal outside the intended directory. The vulnerability affects livebook versions from 0.11.0 before 0.18.7 and from 0.19.0 before 0.19.9. Exploitation requires a victim to open a malicious notebook and trigger the file fetch, with no authentication required for the attacker. The CVSS 4.0 score is 7.0, indicating high severity.

Impact

An attacker can cause arbitrary files to be written on the victim's system running livebook by supplying a malicious notebook. This can lead to unauthorized file creation or modification within any location writable by the livebook process. The attack requires the victim to open the malicious notebook and trigger the file fetch, potentially leading to local compromise or persistence. No privileges or authentication are required by the attacker to prepare the malicious notebook, but the victim must open it. The vulnerability has a high severity rating with a CVSS 4.0 score of 7.0.

Summary

The vulnerability arises from insufficient validation of file entry names in .livemd notebooks imported into livebook. While the UI validates file entry names to be flat filenames, the import path takes the name verbatim, allowing path traversal sequences. When a URL-type file entry is fetched, the resolved path is not properly constrained within the session's temporary directory, allowing files to be written anywhere the livebook process has write permissions. This enables an attacker to write arbitrary files with attacker-controlled content on the victim's system by supplying a crafted notebook. The affected versions are livebook from 0.11.0 up to but not including 0.18.7, and from 0.19.0 up to but not including 0.19.9. There is no indication of an official patch or remediation level provided in the data. No known exploits in the wild have been reported.

CWE-23Relative Path Traversal (opens in a new tab)
Base weaknessOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as ".." that can resolve to a location that is outside of that directory.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Implementation · Input Validation
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174).
Operation · Firewall
Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.3.1 (opens in a new tab)
Attack patterns
Relative Path Traversal (opens in a new tab)
Manipulating Web Input to File System Calls (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

CPE configurations (1)

Description

AI analysisMachine-generated, updated 13 Aug 2026, 17:34 UTC

WeaknessesCWE-23

Technical details

References

Community reviews

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