vulnerability / NVI-00009105 / Revision 3
Authlib accepts an empty HMAC key, allowing JWS/JWT signature forgery (HS256/HS384/HS512)
GitHub lists this reviewed advisory for Authlib. 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.
7.4 high
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
7.4 HIGH (3.1)
security-advisories@github.com severity; no combined Null risk score.
9.1 CRITICAL (3.1)
nvd@nist.gov severity; no combined Null risk score.
0.299%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.22599. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
Authlib
source listed< 1.9.1
Reporter: Cavan Loughran, Celvex Group Inc. Summary Authlib's symmetric (oct) key handling accepts an empty key (empty bytes b'' / empty string '') as a valid HMAC signing and verification key. An empty HMAC key produces a deterministic digest that any party can reproduce, so an attacker who knows (or can cause) the application to verify a token with an empty key can forge arbitrary tokens that pass HS256/HS384/HS512 signature verification. This is the Authlib member of the cross-language empty-HMAC-key family already assigned CVE-2026-44351 (fast-jwt, npm) and CVE-2026-45363 (ruby-jwt, RubyGems). This is DISTINCT from Authlib's existing recent JWT-verification advisories. It is not closed by CVE-2026-27962 / GHSA-wvwj-cvrp-7pv5 (JWS JWK header injection, the key=None case), nor by CVE-2026-28802 / GHSA-7wc2-qxgw-g8gg (alg:none blank-signature bypass), nor by GHSA-5357-c2jx-v7qh (algorithm confusion with asymmetric public keys). Those address header-driven key injection, the none algorithm, and asymmetric-vs-symmetric confusion respectively; none of them rejects a zero-length oct key. Affected versions Authlib <= 1.7.2 (latest release 1.7.2, 2026-05-06). Confirmed present at t
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. FIRST EPSS
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.
- NVD lastModified does not establish freshness of every associated CPE record.
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-8m4g-j4wp-wgcg ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2026-114616 ↗
NIST National Vulnerability Database · official catalog
Observed . This product uses data from the NVD API but is not endorsed or certified by the NVD.
- CVE-2026-114616 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 3 ·
Source facts changed; compare the preserved prior revision.
- Revision 2 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.