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Critical, CVSS 10.0amended

Flyto2 Core: Arbitrary file write via image.download (and other file-writing modules)

CVE-2026-67429GHSA-2956-977x-2w3r

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (flyto-core 2.26.7), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
10.0 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:H
EPSS
  • CVE-2026-67429: 0.57% estimated exploitation activity in the next 30 days; percentile 47.48 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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. This is not isolated to image.download. Most other file-writing modules write to a caller outputpath with no path check at all: image.convert, image.resize, image.crop, image.compress, image.rotate, image.watermark, image.qrcodegenerate, document.excelwrite,…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-2956-977x-2w3r

  2. Revision 2 · amended ·

    Amended from osv record GHSA-2956-977x-2w3r

  3. Revision 1 · created ·

    Published from ghsa record GHSA-2956-977x-2w3r

Agent brief

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# Patch Next advisory brief: CVE-2026-67429

Advisory: Flyto2 Core: Arbitrary file write via image.download (and other file-writing modules)
IDs: CVE-2026-67429, GHSA-2956-977x-2w3r
Record: https://patchnext.com/advisories/cve-2026-67429 (revision 3, source checked 26 Oct 2026, 13:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 10.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: flyto-core 2.26.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI flyto-core: affected < 2.26.7; fixed in 2.26.7

## Suggested inspection (read-only)
- `python -m pip show flyto-core`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on flyto-core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-2956-977x-2w3r (GitHub-reviewed advisory GHSA-2956-977x-2w3r lists affected ranges: PyPI flyto-core >=0 <2.26.7)
- Verified: https://osv.dev/vulnerability/GHSA-2956-977x-2w3r (OSV record GHSA-2956-977x-2w3r lists affected ranges: PyPI flyto-core >=0 <2.26.7 (fixed))

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