# CVE-2023-39326: Denial of service via chunk extensions in net/http > A malicious HTTP sender can cause excessive network reads via chunk extensions, leading to denial of service in Go applications. - **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 6 Dec 2023 - **Updated:** 13 Feb 2025 - **Also known as:** ALSA-2024:1149, AZL-32102, AZL-32124, AZL-37446, AZL-37452, AZL-79114, AZL-98727, BELL-CVE-2023-39326, BIT-golang-2023-39326, DEBIAN-CVE-2023-39326, GHSA-9f76-wg39-x86h, GO-2023-2382, MINI-h49q-gr4h-6v4f, RHSA-2024:1149, RHSA-2024:1244, UBUNTU-CVE-2023-39326 ## What is CVE-2023-39326? CVE-2023-39326 is a medium-severity denial of service vulnerability in Golang Go, published on 6 Dec 2023. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description 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. ## Which versions are affected by CVE-2023-39326? 2 open source packages ship an affected version, including golang and stdlib. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `golang` | Bitnami | All versions | 1.20.12, 1.21.5 | | `stdlib` | Go | All versions | 1.20.12, 1.21.5 | | `skopeo` | AlmaLinux:9 | All versions | 2:1.13.3-4.el9_3 | | `skopeo-tests` | AlmaLinux:9 | All versions | 2:1.13.3-4.el9_3 | | `rhc-worker-script` | Red Hat:enterprise_linux:7::client | All versions | 0:0.6-1.el7_9 | | `rhc-worker-script` | Red Hat:enterprise_linux:7::server | All versions | 0:0.6-1.el7_9 | | `rhc-worker-script` | Red Hat:enterprise_linux:7::workstation | All versions | 0:0.6-1.el7_9 | | `skopeo` | Red Hat:enterprise_linux:9::appstream | All versions | 2:1.13.3-4.el9_3 | | `skopeo-debuginfo` | Red Hat:enterprise_linux:9::appstream | All versions | 2:1.13.3-4.el9_3 | | `skopeo-debugsource` | Red Hat:enterprise_linux:9::appstream | All versions | 2:1.13.3-4.el9_3 | | `skopeo-tests` | Red Hat:enterprise_linux:9::appstream | All versions | 2:1.13.3-4.el9_3 | Products: Golang Go. ## How do I fix CVE-2023-39326? Upgrade golang to a fixed version for your release line: 1.20.12 or 1.21.5. ## Is CVE-2023-39326 being exploited? There is no known exploitation of CVE-2023-39326 in the wild and no public exploit code. ## Other vulnerabilities in Golang Go - [CVE-2020-0601](https://insights.sbomify.com/CVE-2020-0601/): Microsoft Windows CryptoAPI Spoofing (high 8.1, exploited in the wild) - [CVE-2026-27143](https://insights.sbomify.com/CVE-2026-27143/): Missing bound checks can lead to memory corruption in safe Go in cmd/compile (critical 9.8) - [CVE-2024-24790](https://insights.sbomify.com/CVE-2024-24790/): Unexpected behavior from Is methods for IPv4-mapped IPv6 addresses in net/netip (critical 9.8) - [CVE-2023-39320](https://insights.sbomify.com/CVE-2023-39320/): Arbitrary code execution via go.mod toolchain directive in cmd/go (critical 9.8) - [CVE-2023-24540](https://insights.sbomify.com/CVE-2023-24540/): Improper handling of JavaScript whitespace in html/template (critical 9.8) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2023-39326 and fix it if it is affected. What it is: CVE-2023-39326 is a medium-severity denial of service vulnerability in Golang Go, published on 6 Dec 2023. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2023-39326 in the wild and no public exploit code. Affected packages and fixed versions: - golang (Bitnami): affected all versions; fixed in 1.20.12, 1.21.5 - stdlib (Go): affected all versions; fixed in 1.20.12, 1.21.5 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2023-39326/ (Markdown: https://insights.sbomify.com/CVE-2023-39326/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2023-39326 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-39326 - OSV: https://osv.dev/vulnerability/CVE-2023-39326 --- From sbomify Insights: https://insights.sbomify.com/CVE-2023-39326/ Summaries are generated and may contain mistakes; the official description above is the record.