EEF-CVE-2026-66881 CVE-2026-66881 GHSA-r4h8-2xpq-v48g
Path traversal in imported file_entries name allows arbitrary file write via URL-type entry download
- Severity
- 0.0 / 10
- High · CVSS 4.0
- Exploit chance (EPSS)
- 0.61%
- Chance of exploitation in the next 30 days. Higher than 49.19% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-23 Relative Path Traversal
- Fix
0.19.9- Upgrade livebook to this version or later
Description
Summary
Relative Path Traversal vulnerability in livebook-dev livebook allows an attacker-authored notebook to write a file with attacker-controlled content to an arbitrary path.
A .livemd notebook can declare file_entries metadata, each entry carrying a name. Every path that creates a file entry through the user interface validates that name with Livebook.Notebook.validate_file_entry_name/2, which requires a flat filename of alphanumerics, dashes, underscores and dots, ending in an extension. The import path does not: Livebook.LiveMarkdown.Import.file_entry_metadata_to_attrs/1 in lib/livebook/live_markdown/import.ex takes the name verbatim from the notebook source.
For a URL-type file entry, Livebook.Session.file_entry_cache_file/2 in lib/livebook/session.ex resolves that name beneath the session's temporary directory without checking that the result stays inside it, and Livebook.FileSystem.Utils.resolve_unix_like_path/2 collapses parent-directory segments while clamping only at the filesystem root. When the entry's content is requested and no cached copy exists, Livebook fetches the entry's URL and writes the response body to the resolved path, creating parent directories as needed. The attacker therefore controls both the destination and the contents of the written file, which may land anywhere the Livebook process can write. The same missing containment check is present in Livebook.Session.to_attachment_file_entry/2.
A victim who opens an attacker-supplied notebook and causes the entry to be fetched triggers the write within their own authenticated session; the attacker needs no account on the target instance. URL-type entries are also not placed under notebook stamping quarantine on import, so no warning is shown.
This issue affects livebook: from 0.11.0 before 0.18.7 and from 0.19.0 before 0.19.9.
Affected versions
Hex
| Package | Vulnerable | Fixed in |
|---|---|---|
| livebook | >= 0.11.0, < 0.18.7>= 0.19.0, < 0.19.9 |
0.18.70.19.9 |
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.
livebook Hex → 0.19.9
- mix
{:livebook, "~> 0.19.9"} # then: mix deps.update livebook
Severity breakdown
CVSS 4.0 0.0
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
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- High
- Availability (vulnerable system)
- Low
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
CVSS 3.1 8.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- High
Weakness
CWE-23: Relative Path Traversal
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.
How to prevent it
- 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: 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). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked. 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). This includes: realpath() in C getCanonicalPath() in Java GetFullPath() in ASP.NET realpath() or abs_path() in Perl realpath() in PHP
- Operation: 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 [REF-1481].
References
Advisories
Fixes and patches
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| EEF-CVE-2026-66885 Livebook Teams identity callback lacks state binding, allowing login CSRF | Medium | Also affects livebook |
| EEF-CVE-2026-66298 JS-view sandboxed output can synthesize keyboard events to trigger unconfirmed global shortcuts | High | Also affects livebook |
| EEF-CVE-2026-66297 Unescaped deployment environment variables in generated setup commands | High | Also affects livebook |
| EEF-CVE-2026-68746 Livebook Teams identity check fails open when the deployment group is unresolvable, allowing unauthenticated access | High | Also affects livebook |
| GHSA-564w-97r7-c6p9 Livebook Desktop's protocol handler can be exploited to execute arbitrary command on Windows | Critical | Also affects livebook |
| CVE-2026-76519 A vulnerability in the Advanced Malware Protection (AMP) feature of Cisco Secure Email Gateway could allow an unauthenticated, remote attacker to write… | Critical Known exploited | Same weakness, CWE-23 |
| GHSA-83xp-526h-j3ww File Browser: Archive builder turns backslash filenames into path traversal (zip-slip) | Medium | Same weakness, CWE-23 |
| GHSA-c6f4-wj38-m3g3 Snipe-IT vulnerable to directory traversal in displaySig | Medium | Same weakness, CWE-23 |
Credits: Jonatan Kłosko, Jonatan Männchen / EEF, José Valim, Nguyễn Công Tú
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