CVE-2024-53861: pyjwt is a JSON Web Token implementation in Python. An incorrect string comparison is run for `iss` checking, resulting in `"acb"` being accepted for ...

Description

pyjwt is a JSON Web Token implementation in Python. An incorrect string comparison is run for `iss` checking, resulting in `"acb"` being accepted for `"_abc_"`. This is a bug introduced in version 2.10.0: checking the "iss" claim changed from `isinstance(issuer, list)` to `isinstance(issuer, Sequence)`. Since str is a Sequnce, but not a list, `in` is also used for string comparison. This results in `if "abc" not in "__abcd__":` being checked instead of `if "abc" != "__abc__":`. Signature checks are still present so real world impact is likely limited to denial of service scenarios. This issue has been patched in version 2.10.1. All users are advised to upgrade. There are no known workarounds for this vulnerability.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

0.81%

52.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-697

Affected Software

Vendor	Product	Versions
Pyjwt Project	Pyjwt	2.10.0

References

Timeline

Published: Nov 29, 2024
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2024-53861?

pyjwt is a JSON Web Token implementation in Python. An incorrect string comparison is run for `iss` checking, resulting in `"acb"` being accepted for `"_abc_"`. This is a bug introduced in version 2.10.0: checking the "iss" claim changed from `isinstance(issuer, list)` to `isinstance(issuer, Sequence)`. Since str is a Sequnce, but not a list, `in` is also used for string comparison. This results in `if "abc" not in "__abcd__":` being checked instead of `if "abc" != "__abc__":`. Signature checks are still present so real world impact is likely limited to denial of service scenarios. This issue has been patched in version 2.10.1. All users are advised to upgrade. There are no known workarounds for this vulnerability.

How severe is CVE-2024-53861?

CVE-2024-53861 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.81% probability of exploitation in the next 30 days.

How do I fix CVE-2024-53861?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.