CVE-2026-69249: python-cryptography: Duplicate self-signed intermediates can cause exponential path-building

Vulnerability summary

CVE-2026-69249 is a high (CVSS 8.7) Uncontrolled Resource Consumption vulnerability in pyca cryptography. EPSS estimates a 0.26% chance of exploitation in the next 30 days, higher than 18% of scored vulnerabilities.

Timeline

1. 03-08-2026
   PublishedVulnerability first disclosed.
2. 04-09-2026
   Last modifiedVulnerability information updated.

Description

python-cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. In versions 42.0.0 through 48.0.0, when resolving invalid certificate chains that include duplicate copies of self-signed certificates, the processing recursively invokes the same candidate, leading to an exponential blowup. Although the limitation that the chain depth cannot exceed a specified maximum depth prevents unbounded recursion and guarantees termination, an attacker-controlled certificate chain can lead the processing to easily take more than 5s to reject in testing. This amplification could form the basis for a resource exhaustion denial of service attack. The core issue arises in the recursive nature of build_chain_inner, which does not de-duplicate against previously analyzed candidates. As the correctness of validation is not affected, the integrity of a system cannot be compromised through this vector, only its availability. This issue is fixed in 49.0.0.

• CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.