vulnerability / NVI-00017735 / Revision 1
Lemur: JWT verifier honors attacker-supplied alg, enabling ATO
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.
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.
4.8 medium
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
Lemur 1.9.0: JWT verifier trusts attacker-supplied alg from token header — defense-in-depth gap; chain-dependent ATO with secret disclosure Vulnerability Summary Field | Value -- | -- Title | Lemur 1.9.0: JWT verifier trusts attacker-supplied alg from token header — defense-in-depth gap; chain-dependent ATO with secret disclosure Component | lemur/lemur/auth/service.py:130-137 CWE | CWE-347 (Improper Verification of Cryptographic Signature) Attack Prerequisite | Defense-in-depth gap on its own — no single-request exploit against PyJWT 2.x. Single-request ATO requires a separate disclosure issue that leaks LEMUR_TOKEN_SECRET, or a future migration to asymmetric signing without fixing this sink. Affected Versions | github.com/Netflix/lemur __version__ = "1.9.0". Same code present in every prior release that has the auth/service.py:130 block. Executive Summary The Lemur JWT verifier reads the alg heade
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-r9gp-7f88-9r54 ↗
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.