vulnerability / NVI-00015124 / Revision 1
Thumbor proportion filter allows unbounded post-transform resize leading to remote DoS
GitHub lists this reviewed advisory for thumbor. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
7.5 high
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
thumbor
source listed<= 7.7.7
### Summary Thumbor's `filters:proportion()` filter does not enforce an upper bound on `` and runs in the post-transform phase. An attacker can trigger extremely large resizes (CPU/memory exhaustion) and cause denial of service. ### Details - Filter implementation: `thumbor/filters/proportion.py` - `value` is parsed as a float (`BaseFilter.DecimalNumber`) with no maximum. - The filter computes `new_width = source_width * value` and `new_height = source_height * value` and then calls `engine.resize(new_width, new_height)`. - Execution phase: `proportion` runs in the default POST_TRANSFORM phase (after the main transform pipeline). This means it can effectively bypass request-level size clamping that happens earlier in the request lifecycle (e.g., `MAX_WIDTH`/`MAX_HEIGHT` applied to `req.width/req.height`). Documentation states the `percentage` argument should be `0.0 to 1.0` (`docs/proportion.rst`), but the implementation does not enforce this constraint. ### PoC #### Preconditions - The `proportion` filter is enabled (it is enabled by default via `BUILTIN_FILTERS`). - Either: - `/unsafe/` URLs are allowed (`ALLOW_UNSAFE_URL=True`, common default in some deplo
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-phj3-59pf-cp83 ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.