vulnerability / NVI-00014987 / Revision 1
PyJWKClient unbounded JWKS endpoint requests via attacker-controlled kid values (DoS)
GitHub lists this reviewed advisory for pyjwt. 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.
3.7 low
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.
pyjwt
source listed>= 2.0.0, <= 2.12.1
> [!NOTE] > The vulnerability surfaces only when a JWKS fetch fails; an attacker can attempt to provoke that with sustained unknown-kid traffic, but the outcome depends on upstream JWKS-endpoint behavior (rate limiting, transient errors) which is beyond the attacker's control. Impact is reduced auth availability until the next successful fetch, not complete denial of service. ## Summary PyJWKClient.get_signing_key() forces a fresh HTTP request to the JWKS endpoint for every JWT with an unknown kid value, with no rate limiting. Since kid comes from the unverified token header, an attacker can trigger unlimited outbound requests. Additionally, fetch_data() finally block clears the JWKS cache on network error. ## Root Cause jwt/jwks_client.py:172-198 - get_signing_key(kid) calls get_signing_keys(refresh=True) for unknown kids, bypassing TTL cache with no cooldown. jwt/jwks_client.py:120-122 - finally block writes None to cache on error, clearing valid data. ## Impact - DoS against JWKS endpoint (unlimited requests per invalid token) - DoS against application (network I/O latency) - Cascading failure (rate limiting clears cache, breaking legitimate auth) ## Suggested Fix 1. Add r
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.
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-fhv5-28vv-h8m8 ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.