S3 File System security updates, in plain English

S3 File System

17,818 sites report using it · on drupal.org · 1 security update explained here

This module stores website files in Amazon cloud storage instead of on the web server.

Below is every security update for S3 File System that this site has covered, newest first. Each one says who could exploit it, whether it applies to your site, how urgent it is, and what to tell your developer. If your site uses this module and you are not sure which version, that is the first question to ask whoever looks after it.

S3 File System

Moderately critical · 17,818 sites report using it · SA-CONTRIB-2026-279 · on drupal.org · Week of 28 October 2026

The module mixes up the context of different file uploads happening at the same time. Files could be uploaded with the wrong access rights or become corrupted. Someone could read or change data they should not have access to.

Who could do thisAnyone visiting the site. No login needed.
Does it apply to youAn attacker can trigger multiple file operations at the same time and the site uses specific private file settings or custom code modifications.
Has it been used in attacksNo sign of it.
How urgentDrupal rates this moderately critical. Include it in your next routine update, within the month.

Tell your developerUpdate S3 File System to 8.x-3.12.

For developers: what the fix changed

The fix adds a resetContextOptions method to src/StreamWrapper/S3fsStream.php and calls it after file operations like stream_open, stream_flush, and rename to reset the stream context options.

Also in this release The release also updates the README file with bucket configuration recommendations.

8.x-3.11 to 8.x-3.12 1 commit, 2 files.

README.txt +62 −0
src/StreamWrapper/S3fsStream.php +30 −3 fix

Full diff, 8.x-3.11 to 8.x-3.12

The comparison is against the release immediately before the fix. If your site is on an older release, more will have changed.

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Tell me who you are, what your organisation does, and what you need. That might be a Drupal site that needs looking after, an upgrade to get done before December, or an agency that needs Drupal cover.

If I can help, I'll say so and suggest a call. If I can't, I'll tell you straight away rather than waste your time.

For context: I work mainly with UK membership bodies, charities and research organisations, and with the agencies that look after their websites. Not recruiters.

Or start smaller and connect with me on LinkedIn. That's where I post what I find digging around in charity and grants data, and where the free tools turn up first.

S3 File System

S3 File System

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