CVE-2023-39326: Golang Go

Medium severity, CVSS 5.3. EPSS: 1.2% chance of exploitation in the next 30 days.

A malicious HTTP sender can use chunk extensions to cause a receiver reading from a request or response body to read many more bytes from the network than are in the body. A malicious HTTP client can further exploit this to cause a server to automatically read a large amount of data (up to about 1GiB) when a handler fails to read the entire body of a request. Chunk extensions are a little-used HTTP feature which permit including additional metadata in a request or response body sent using the chunked encoding. The net/http chunked encoding reader discards this metadata. A sender can exploit this by inserting a large metadata segment with each byte transferred. The chunk reader now produces an error if the ratio of real body to encoded bytes grows too small.

Affected products

• Golang Go: before 1.20.12 (fixed in 1.20.12); from 1.21.0-0, before 1.21.5 (fixed in 1.21.5)

Published 2023-12-06. Last modified 2026-06-17.