Is CVE-2026-101918 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-101918 being exploited in the wild.

How severe is CVE-2026-101918?

Medium severity, with a CVSS score of 5.3, published 28 September 2026.

Which products and versions are affected?

PyJWT 2.0.0a1 to 2.15.0; pyjwt (PyPI) >= 2.0.0a1, <= 2.14.0, ECOSYSTEM:introduced=2.0.0a1,fixed=2.15.0.

Is there a fix for CVE-2026-101918?

Yes. pyjwt (PyPI): upgrade to 2.15.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-101918 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-101918?

Check whether you run PyJWT or pyjwt (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-101918: PyJWT recursion error denial of service

Q: Is there a fix for CVE-2026-101918?

Yes. pyjwt (PyPI): upgrade to 2.15.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: How is CVE-2026-101918 attacked?

It is attacked over the network, in a software library.

Q: Am I affected by CVE-2026-101918?

Check whether you run PyJWT or pyjwt (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-101918 · Severity: medium · CVSS 5.3 · Published 2026-09-28

PyJWT, a Python library that validates digital tokens used for secure authentication and authorization, fails to properly handle malicious tokens with deeply nested data structures. An attacker can send a specially crafted token that causes the application to crash with an HTTP 500 error, disrupting service for legitimate users without requiring authentication.

Technologies: PyJWT, pyjwt (PyPI). Vendors: PyJWT, PyPI.

Quick answers

Is CVE-2026-101918 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-101918 being exploited in the wild.
How severe is CVE-2026-101918?: Medium severity, with a CVSS score of 5.3, published 28 September 2026.
Which products and versions are affected?: PyJWT 2.0.0a1 to 2.15.0; pyjwt (PyPI) >= 2.0.0a1, <= 2.14.0, ECOSYSTEM:introduced=2.0.0a1,fixed=2.15.0.
Is there a fix for CVE-2026-101918?: Yes. pyjwt (PyPI): upgrade to 2.15.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-101918 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-101918?: Check whether you run PyJWT or pyjwt (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

pyjwt (PyPI): upgrade to 2.15.0 or later
```
pip install "pyjwt>=2.15.0"
```

Technical details

PyJWT versions 2.0.0a1 through 2.15.0 catch ValueError exceptions during JSON payload parsing but do not catch RecursionError exceptions. An attacker can supply a JWT with a recursively nested payload that triggers RecursionError when passed to json.loads(), bypassing the library's documented exception handling and causing an unhandled exception. The vulnerability affects PyJWKClient.get_signing_key_from_jwt and jwt/api_jwt.py with verify_signature=False, allowing unauthenticated denial of service via network-supplied malicious tokens.

Affected products

PyJWT PyJWT 2.0.0a1 to 2.15.0

Identifiers

CVE-2026-101918
GHSA-42vr-xj54-vc7v
PYSEC-2026-4141

Timeline

2026-09-28: disclosed
2026-09-23: patched: Version 2.15.0 released with fix

References

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