CVE-2024-53861: pyjwt — Exploit & Fix

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.

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CVSS v3.1 Score

2.2

LOW

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

Weakness Type (CWE)

CWE-697 CWE-697

Affected Products

Vendor	Product	Versions
pyjwt_project	pyjwt	All

References

Advisories & Patches

https://github.com/jpadilla/pyjwt/commit/1570e708672aa9036bc772476beae8bfa48f4131#diff-6893ad4a1c5a36b8af3028db8c8bc3b62418149843fc382faf901eaab008e380R366 https://github.com/jpadilla/pyjwt/commit/33022c25525c1020869c71ce2a4109e44ae4ced1 https://github.com/jpadilla/pyjwt/security/advisories/GHSA-75c5-xw7c-p5pm

Exploits

https://github.com/jpadilla/pyjwt/security/advisories/GHSA-75c5-xw7c-p5pm

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. It has a CVSS v3.1 base score of 2.2 (LOW).

How severe is CVE-2024-53861? +

CVE-2024-53861 has a CVSS v3.1 score of 2.2 out of 10, rated LOW. This is a low-severity vulnerability with limited impact.

What products are affected by CVE-2024-53861? +

CVE-2024-53861 affects products from pyjwt_project, specifically: pyjwt. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2024-53861? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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