vulnerability / NVI-00017844 / Revision 1
Lemur: Incomplete fix for GHSA-v2wp-frmc-5q3v -- ACME authority update endpoint allows non-admin to replace `acme_url` with internal IP, bypassing allowlist
GitHub lists this reviewed advisory for lemur. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
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01 / Meaning
Why it matters
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7.7 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.
lemur
source listed<= 1.9.2
### Summary The fix for GHSA-v2wp-frmc-5q3v added `_validate_acme_url()` to reject `acme_url` values not in `ACME_DIRECTORY_HOST_ALLOWLIST`, but the validation is only called at **authority creation time** (POST). The authority **update** endpoint (`PUT /api/1/authorities/`) accepts and stores arbitrary `options` -- including a modified `acme_url` -- without invoking the allowlist check. Any user with an authority role (granted by an admin to allow issuing certificates via that authority) can therefore overwrite the stored `acme_url` with an internal IP or IMDS endpoint. The next certificate issuance via that authority causes Lemur's backend to fetch the attacker-controlled URL, achieving SSRF. ### Details **Where the fix lives (POST path -- protected):** `lemur/plugins/lemur_acme/plugin.py` lines 333-337 (ACMEIssuerPlugin.create_authority): ```python for option in plugin_options: if option.get("name") == "certificate": acme_root = option.get("value") if option.get("name") == "acme_url": _validate_acme_url(option.get("value", "")) # allowlist enforced ``` `_validate_acme_url` at line 35: ```python def _validate_acme_url(url): """Reject acme_ur
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-v5rc-cpwc-cfpr ↗
GitHub Advisory Database · vendor advisory
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- Revision 1 ·
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