# CVE-2026-69249: Pyca Cryptography exponential path-building in X.509 verification

Source: https://junglewise.ai/threats/cve-2026-69249-pyca-cryptography-exponential-path-building-in-x-509-verification  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-03. Updated: 2026-08-03  
License: CC BY 4.0 with a link back

CVE-2026-69249 · Severity: high · CVSS 4 · Published 2026-08-03

A vulnerability in the popular Python 'cryptography' library can allow an attacker to crash or slow down a service by providing a specially crafted security certificate. The library fails to efficiently process certain types of invalid certificate chains, leading to excessive CPU usage. This can result in a denial-of-service (DoS) where the application becomes unresponsive to legitimate users.

Technologies: [cryptography (PyPI)](https://junglewise.ai/threats/technologies/cryptography). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-69249 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-69249 being exploited in the wild.

**How severe is CVE-2026-69249?** High severity, with a CVSS score of 4, published 3 August 2026.

**Which products and versions are affected?** cryptography (PyPI) <= 48.0.0, ECOSYSTEM:introduced=0,fixed=49.0.0, ECOSYSTEM:introduced=42.0.0,fixed=49.0.0.

**Is there a fix for CVE-2026-69249?** Yes. cryptography (PyPI): upgrade to 49.0.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-69249 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-69249?** Check whether you run cryptography (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- cryptography (PyPI): upgrade to 49.0.0 or later

  ```sh
  pip install "cryptography>=49.0.0"
  ```


## Technical details

A resource exhaustion vulnerability exists in the X.509 path-building logic of the cryptography library. The `build_chain_inner` function, which is part of the certificate verification process, recursively invokes itself without de-duplicating previously analyzed candidates when resolving invalid chains with duplicate self-signed certificates. While a maximum chain depth exists to prevent infinite recursion, the exponential growth in path-building attempts allows an attacker to trigger significant processing delays (e.g., >5 seconds for a small chain). This can be exploited remotely by providing a crafted certificate chain to any service performing X.509 validation using the affected library. The issue is fixed in version 49.0.0 by tracking and skipping already-seen valid issuers during recursion.

## Affected products

- pyca cryptography <= 48.0.0

## Identifiers

- CVE-2026-69249
- GHSA-jwv3-5hgf-82ww
- PYSEC-2026-3553

## Timeline

- 2026-07-31: advisory: GitHub Advisory published
- 2026-08-03: disclosed: CVE-2026-69249 disclosed
- 2026-08-03: patched: Fixed in version 49.0.0

## References

- [https://api.github.com/users/sjudson](https://api.github.com/users/sjudson)
- [https://github.com/sjudson](https://github.com/sjudson)
- [https://api.github.com/users/sjudson/gists%7B/gist_id%7D](https://api.github.com/users/sjudson/gists%7B/gist_id%7D)
- [https://api.github.com/users/sjudson/repos](https://api.github.com/users/sjudson/repos)
- [https://avatars.githubusercontent.com/u/20324824?v=4](https://avatars.githubusercontent.com/u/20324824?v=4)
- [https://api.github.com/users/sjudson/events%7B/privacy%7D](https://api.github.com/users/sjudson/events%7B/privacy%7D)

## Related threats

- [pyca cryptography improper certificate validation in Name Constraints](https://junglewise.ai/threats/cve-2026-69248-pyca-cryptography-improper-certificate-validation-in-name)
- [pyca cryptography Bleichenbacher oracle in PKCS#7 decryption](https://junglewise.ai/threats/cve-2026-69247-pyca-cryptography-bleichenbacher-oracle-in-pkcs-7-decryption)
- [PYSEC-2026-1284 - Vulnerable OpenSSL included in cryptography wheels](https://junglewise.ai/threats/cve-2024-12797-vulnerable-openssl-included-in-cryptography-wheels)
- [PYSEC-2026-1283 - Python Cryptography package vulnerable to Bleichenbacher timing oracle attack](https://junglewise.ai/threats/cve-2023-50782-python-cryptography-package-vulnerable-to-bleichenbacher-timing)
- [Pyca Cryptography vulnerable OpenSSL in pre-compiled wheels](https://junglewise.ai/threats/pyca-cryptography-vulnerable-openssl-in-pre-compiled-wheels-d6089b68)