GHSA-j4h9-pm27-4rfw CVE-2026-54134 PYSEC-2026-2687
OctoPrint has possible file exfiltration via query parameters on upload endpoints
- Severity
- 0.0 / 10
- High · CVSS 4.0
- Exploit chance (EPSS)
- 0.32%
- Chance of exploitation in the next 30 days. Higher than 25.45% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Fix
1.11.8- Upgrade octoprint to this version or later
Description
Impact
OctoPrint versions up until and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from. This vulnerability was already reported as GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 but the fix provided in OctoPrint 1.11.2 turned out to be incomplete.
The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host after an attempted server restart. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.
Patches
The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.
Details
OctoPrint's web application is implemented in Flask, but uploads are first intercepted by a custom upload handler built on Tornado that sits in front of it. The handler streams the upload to a temporary file on disk - so files larger than the available memory can be uploaded - and rewrites the request, adding internal form fields that tell Flask where to find that temporary file.
These fields are reserved and meant to be set only by the upload handler, never by the client. The previous fix from GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 stripped them from the request received from the client when they were sent as multipart form fields, yet they could still reach Flask through other channels: as plain query parameters, or - since the Tornado handler and Flask did not parse requests identically - smuggled in via several "parser differentials" that looked harmless to the handler while Flask still saw the injected fields. Any of these let an attacker make OctoPrint treat an arbitrary file on the host as a freshly uploaded one and move it into the upload folder.
The following endpoints in OctoPrint are affected:
/api/files/{local|sdcard}/api/languages/plugin/backup/restore/plugin/pluginmanager/upload_file
Further upload endpoints in third party plugins might be affected too.
The fix rejects requests carrying any of the reserved fields, aligns the Tornado handler's request parsing with Flask's (Werkzeug) to avoid any differential parsing, and re-validates the request rewritten by Tornado before forwarding it to Flask.
Credits
This vulnerability was discovered and responsibly disclosed to OctoPrint by Koh Jun Sheng and Jacopo Tediosi.
Timeline
2026-06-04: Report received 2026-06-04: Report acknowledged 2026-06-08: Report verified 2026-06-17: Fix ready for 1.11.x 2026-06-22: Fix ported to 2.0.0 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3
Affected versions
PyPI
| Package | Vulnerable | Fixed in |
|---|---|---|
| octoprint | < 1.11.8 |
1.11.8 |
| octoprint | >= 2.0.0rc1, < 2.0.0rc3 |
2.0.0rc3 |
| octoprint | < 1.11.8>= 2.0.0rc1, < 2.0.0rc3 |
1.11.82.0.0rc3 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
octoprint PyPI → 1.11.8
- pip
pip install --upgrade "octoprint>=1.11.8"- poetry
poetry add "octoprint>=1.11.8"- uv
uv add "octoprint>=1.11.8"
Severity breakdown
CVSS 4.0 0.0
CVSS:4.0/AV:A/AC:L/AT:N/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N
- Attack vector
- Adjacent
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- Low
- User interaction
- None
- Confidentiality (vulnerable system)
- High
- Integrity (vulnerable system)
- Low
- Availability (vulnerable system)
- None
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
Weakness
CWE-436: Interpretation Conflict
Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B's state.
CWE-73: External Control of File Name or Path
The product allows user input to control or influence paths or file names that are used in filesystem operations.
How to prevent it
- Architecture and Design: When the set of filenames is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames, and reject all other inputs. For example, ID 1 could map to "inbox.txt" and ID 2 could map to "profile.txt". Features such as the ESAPI AccessReferenceMap provide this capability.
- Architecture and Design, Operation: Run your code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict all access to files within a particular directory. Examples include the Unix chroot jail and AppArmor. In general, managed code may provide some protection. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of your application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.
- Architecture and Design: For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
- Implementation: 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. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. When validating filenames, use stringent allowlists that limit the character set to be used. If feasible, only allow a single "." character in the filename to avoid weaknesses such as CWE-23, and exclude directory separators such as "/" to avoid CWE-36. Use a list of allowable file extensions, which will help to avoid CWE-434. Do not rely exclusively on a filtering mechanism that removes potentially dangerous characters. This is equivalent to a denylist, which may be incomplete (CWE-184). For example, filtering "/" is insufficient protection if the filesystem also supports the use of "\" as a directory separator. Another possible error could occur when the filtering is applied in a way that still produces dangerous data (CWE-182). For example, if "../" sequences are removed from the ".../...//" string in a sequential fashion, two instances of "../" would b
- Implementation: Use a built-in path canonicalization function (such as realpath() in C) that produces the canonical version of the pathname, which effectively removes ".." sequences and symbolic links (CWE-23, CWE-59).
- Installation, Operation: Use OS-level permissions and run as a low-privileged user to limit the scope of any successful attack.
- Operation, Implementation: If you are using PHP, configure your application so that it does not use register_globals. During implementation, develop your application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.
- Testing: Use tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session. These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.
References
Advisories
Packages
Other links
- github.com/OctoPrint/OctoPrint/security/advisories/GHSA-j4h9-pm27-4rfw
- github.com/pypa/advisory-database/tree/main/vulns/octoprint/PYSEC-2026-2687.yaml
- github.com/OctoPrint/OctoPrint/commit/579148beeb6d6e9b3d41b1cf32309b47218ed380
- github.com/OctoPrint/OctoPrint/commit/8e3348197db867c30a32d13984f0bd0d664be413
- github.com/OctoPrint/OctoPrint/releases/tag/1.11.8
- github.com/OctoPrint/OctoPrint/releases/tag/2.0.0rc3
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-p6qx-ghxm-389h OctoPrint has XSS in its Suppressed Command Notifications | Medium | Also affects octoprint |
| GHSA-xg4x-w2j3-57h6 OctoPrint has Timing Side-Channel Vulnerability in API Key Authentication | Medium | Also affects octoprint |
| GHSA-crvm-xjhm-9h29 OctoPrint vulnerable to XSS in Action Commands Notification and Prompt | Medium | Also affects octoprint |
| GHSA-49mj-x8jp-qvfc OctoPrint is Vulnerable to RCE Attacks via Unsanitized Filename in File Upload | High | Also affects octoprint |
| GHSA-9wj4-8h85-pgrw OctoPrint Vulnerable to Denial of Service through malformed HTTP request in OctoPrint | Medium | Also affects octoprint |
| GHSA-m9jh-jf9h-x3h2 OctoPrint vulnerable to possible file extraction via upload endpoints | Medium | Also affects octoprint |
| GHSA-qw93-h6pf-226x OctoPrint Authenticated Reverse Proxy Page Authentication Bypass | Medium | Also affects octoprint |
| GHSA-cc6x-8cc7-9953 OctoPrint has API key access in settings without reauthentication | Medium | Also affects octoprint |
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