VulnerabilityPublished 6 Oct 2026Updated 29 Oct 2026

CVE-2026-103263: Tornado · StaticFileHandler follows symlinks outside static root (path traversal)

Affects jupyterlabSource GCVE Database

Compare

Authoritative record:CVE-2026-103263· High 8.2

Not known to be exploited · CVSS 8.2 High : upgrade to 4.6.4 soon.

Data as of 30 Oct 2026, 08:59 UTC

CVSS 4.0 base score

8.2High

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

Patch: Available – fixed in 4.6.4

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: Present
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: High
Vulnerable system integrity: None
Vulnerable system availability: None
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: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
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: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: High: There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
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: 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 1 Oct 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 4.6.4.

Affected software

Product	Affected	Fixed in
Homebrewjupyterlab`pkg:brew/jupyterlab`Other threats	Affected >=1.2.0 <4.6.4	Fixed in 4.6.4

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 Tornado version 4.6.4 that fixes this vulnerability by properly resolving symlinks during path validation. Users should upgrade to version 4.6.4 or later. Until patched, avoid placing symlinks inside the static directory that point outside it, and ensure uploaded files do not include symlinks. No other specific mitigations are indicated by the vendor advisory.

Description

A path traversal vulnerability in Tornado's StaticFileHandler allows unauthenticated attackers to read arbitrary files on the server by exploiting symbolic links inside the static root directory. This occurs because the handler uses os.path.abspath() which does not resolve symlinks when validating paths, enabling attackers to access files outside the intended directory. The vulnerability affects applications serving user-uploaded content or using build pipelines that create symlinks in the static directory. A fix is available in Tornado version 4.6.4.

Impact

An unauthenticated remote attacker can read any file accessible by the Tornado process user by exploiting symlinks in the static directory. This can lead to disclosure of sensitive information including application secrets, private TLS keys, database credentials, system files like /etc/shadow, SSH keys, or source code. The impact depends on the permissions of the Tornado process and the presence of symlinks pointing outside the static root.

Summary

The vulnerability exists in tornado.web.StaticFileHandler due to improper path validation. The handler uses os.path.abspath() to check if a requested file path is within the static root directory, but this function does not resolve symbolic links. Consequently, a symlink inside the static directory pointing outside it passes the validation check. However, subsequent file existence and file type checks follow symlinks, allowing access to files outside the static root. An attacker can exploit this by creating or leveraging a symlink pointing to sensitive files such as /etc/passwd or application secrets. The correct fix is to replace os.path.abspath() with os.path.realpath() to validate the real resolved path against the static root. This vulnerability affects Tornado versions >=1.2.0 and <4.6.4 and is patched in 4.6.4.

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 30 Oct 2026, 08:59 UTC

Technical details

References

Community reviews

Related threats