An issue was discovered in webargs before 5.1.3, as used with marshmallow and other products. JSON parsing uses a short-lived cache to store the parsed JSON body. This cache is not thread-safe, meaning that incorrect JSON payloads could have been parsed for concurrent requests.

References

• https://nvd.nist.gov/vuln/detail/CVE-2019-9710
• marshmallow-code/webargs#371
• GHSA-8554-jxcw-454q
• https://webargs.readthedocs.io/en/latest/changelog.html#id20