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Fixing “Decompressed delta part exceeds configured limit” in Flatpak

Ezra Flatpak

This error occurs when Flatpak tries to apply an OCI delta update (a small patch to an existing app bundle) but the decompressed delta part is larger than the configured limit. This can happen due to either:

  • Corrupted or oversized delta files in the update stream.
  • Flatpak version bugs in older versions (≤ 1.18.0) that incorrectly handle delta sizes Github.

Why it happens

  • Flatpak uses delta updates to reduce bandwidth and storage by only sending changes to an existing app bundle.
  • In older Flatpak versions, a bug in the OCI delta stream parser could cause incorrect size limits when reading delta parts, leading to the “exceeds configured limit” error Github.
  • This is not a general network or app issue — it’s a Flatpak client bug in the delta handling code.

Official fix

The vulnerability and bug were patched in Flatpak 1.18.1 with changes to:

  • Use gsize consistently for delta sizes (preventing 32-bit truncation on 32-bit systems) Github.
  • Limit delta path lengths to PATH_MAX.
  • Avoid overflow in delta data reading.

Action:
Upgrade Flatpak to 1.18.1 or later:

# On most distrossudo dnf update flatpak# orsudo apt update && sudo apt install --only-upgrade flatpak

If you’re on a distro that doesn’t have 1.18.1 yet, check the backports or wait for a package update.

Workarounds if you can’t upgrade immediately

  1. Disable delta updates for the affected app:

    bash flatpak override --user --no-deltas org.mozilla.firefox

    This forces Flatpak to download the full bundle instead of deltas, avoiding the oversized delta check openSUSE Forums.

  2. Reinstall the app:

    bash flatpak uninstall org.mozilla.firefoxflatpak install flathub org.mozilla.firefox

    This clears any corrupted delta cache.

  3. Clear Flatpak cache:

    bash flatpak repair

    This rebuilds bundles and can fix corrupted delta parts cloudhousetechnologies.com.

Security note

The underlying issue (CVE-like vulnerability) could allow buffer overflows if an attacker controls an OCI registry, so upgrading is the safest long-term fix Github.

Summary:

Upgrade to Flatpak 1.18.1+ to resolve the bug, or disable deltas for the app if you can’t upgrade yet. Clearing the cache and reinstalling the app can also work as a temporary fix.