Security Digest · Vulnerability record
CVE-2026-67429: Flyto2 Core: Arbitrary file write via image.download (and other file-writing modules)
Flyto2 Core is an execution kernel for automation and AI-agent workflows.
CVSS 10.0 Critical EPSS 0.8% · p55
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.8%, percentile 55: FIRST’s model estimates a 0.8% chance of exploitation activity in the next 30 days, higher than 55% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes
flyto-core(PyPI) < 2.26.7, fixed in 2.26.7. Check your lockfile, including transitive dependencies.
What it is
Flyto2 Core is an execution kernel for automation and AI-agent workflows. Prior to 2.26.6, image.download and related file-writing modules use caller-controlled outputdir instead of validatepathwithenvconfig and its FLYTOSANDBOXDIR confinement, allowing attacker-controlled response bytes to be written to arbitrary filesystem paths the process can access. This issue is fixed in version 2.26.6.
From the GitHub advisory
Summary
image.download fetches a URL and writes the response to disk. It does not use the central path guard (validatepathwithenvconfig, which confines writes to FLYTOSANDBOXDIR); instead it confines the output to outputdir, but outputdir is itself a caller parameter. Since the attacker sets both the target and the base it is checked against, the check is meaningless, and attacker-controlled bytes (the HTTP response) land at any absolute path the process can write.
Affected code
src/core/modules/atomic/image/download.py:
commonpath is used correctly, but the base is caller-supplied, so setting outputdir='/' passes any target. file.write, by contrast, uses validatepathwithenvconfig() and stays inside FLYTOSANDBOXDIR.
Weakness type: CWE-22, CWE-73.
Product: flyto-core (PyPI) · Assigned by: GitHub_M · Published: 2026-07-29
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| PyPI | flyto-core | < 2.26.7 | 2.26.7 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| flytohub | flyto-core | < 2.26.6 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 3.1 | 10 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H |
| GitHub | 3.1 | 10.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: changed (can affect other components)
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 0.77% probability of exploitation activity in the next 30 days; percentile 55.
Timeline
- — CVE record last updated
- — CVE record published by GitHub_M
- — GitHub-reviewed advisory GHSA-2956-977x-2w3r published (critical)
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-2956-977x-2w3r github.com
- CVE.org record CVE-2026-67429 cve.org
- NVD entry CVE-2026-67429 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com
- github.com github.com