CVE-2026-69249
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.
- Score
- CVSS 4.0 8.7 High
- Status
- Awaiting Analysis - security-advisories@github.com
- Published
- 2026-08-03
- Last modified
- 2026-10-23
- Weaknesses
- CWE-400
Affected products
References
- https://github.com/pyca/cryptography/security/advisories/GHSA-jwv3-5hgf-82ww
- https://github.com/pyca/cryptography/pull/14960
- https://github.com/pyca/cryptography/commit/3763aa79b
- https://github.com/pyca/cryptography/commit/4a12cf49675a184e47f912b00b04f3a629283582
- https://github.com/pypa/advisory-database/tree/main/vulns/cryptography/PYSEC-2026-3553.yaml
