vulnerability / NVI-00012913 / Revision 1
Thumbor treats ALLOWED_SOURCES string patterns as unescaped regex, allowing hostname bypass via wildcard dot
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.
8.2 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 The `ALLOWED_SOURCES` configuration is meant to restrict which hosts Thumbor's HTTP loader may fetch images from. Plain-string entries in that list (the overwhelming majority of real-world and documented configurations) are passed directly to `re.match()` without escaping. Because `.` is a regex wildcard, every dot in a domain name becomes a bypass vector: `s.glbimg.com` silently matches `sXglbimgYcom`, `sAglbimg.com`, and any other hostname that differs only at a dot position. This undermines the primary SSRF defence that `ALLOWED_SOURCES` is intended to provide. ## Affected component `thumbor/loaders/http_loader.py` — `validate()` ## Proof of concept ```python import re from thumbor.config import Config from thumbor.context import Context from thumbor.loaders import http_loader as loader config = Config() config.ALLOWED_SOURCES = ["s.glbimg.com"] # typical user config ctx = Context(None, config, None) # These should be blocked — both return True due to the unescaped dot print(loader.validate(ctx, "http://sXglbimgYcom/secret.jpg")) # True ← bypass print(loader.validate(ctx, "http://sAglbimg.com/secret.jpg")) # True ← bypass # Legitimate origin — correctly al
03 / Response
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- investigate
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04 / Limits
What this report cannot establish
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05 / Provenance
Sources you can inspect
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- GHSA-6x26-6r6f-m537 ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
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