SB2025103163 - Two denial of service vulnerabilities in Authlib

Description

This security bulletin contains information about 2 vulnerabilities.

1) Resource exhaustion (CVE-ID: CVE-2025-61920)

CWE-ID: CWE-400 - Resource exhaustion

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to the way the Authlib's JOSE implementation handles untrusted input. A remote non-authenticated attacker can send overly large amount of data via unbounded JWS/JWT header and signature segments to the application and consume memory and CPU resources, leading to a denial of service condition. 

2) Resource exhaustion (CVE-ID: CVE-2025-62706)

CWE-ID: CWE-400 - Resource exhaustion

CVSSv4: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote user to perform a denial of service (DoS) attack.

The vulnerability exists due to Authlib's JWE zip=DEF path performs unbounded DEFLATE decompression. A very small ciphertext can expand into tens or hundreds of megabytes on decrypt. A remote user can supply decryptable tokens and exhaust memory and CPU resources, leading to denial of service conditions. 

Remediation

Install update from vendor's website.

References

• https://github.com/authlib/authlib/commit/867e3f87b072347a1ae9cf6983cc8bbf88447e5e
• https://github.com/authlib/authlib/security/advisories/GHSA-pq5p-34cr-23v9
• https://github.com/authlib/authlib/commit/e0863d5129316b1790eee5f14cece32a03b8184d
• https://github.com/authlib/authlib/security/advisories/GHSA-g7f3-828f-7h7m