# CVE-2026-33320: Dasel has unbounded YAML alias expansion in dasel leads to CPU/memory denial of service > An attacker can cause CPU and memory exhaustion in Dasel by supplying malicious YAML input, leading to a denial of service. - **Severity:** Medium 6.2 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 24 Mar 2026 - **Updated:** 26 Mar 2026 - **Also known as:** GHSA-4fcp-jxh7-23x8, GO-2026-4768, UBUNTU-CVE-2026-33320 ## What is CVE-2026-33320? CVE-2026-33320 is a medium-severity denial of service vulnerability in TomWright dasel, published on 24 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description Dasel is a command-line tool and library for querying, modifying, and transforming data structures. Starting in version 3.0.0 and prior to version 3.3.1, Dasel's YAML reader allows an attacker who can supply YAML for processing to trigger extreme CPU and memory consumption. The issue is in the library's own `UnmarshalYAML` implementation, which manually resolves alias nodes by recursively following `yaml.Node.Alias` pointers without any expansion budget, bypassing go-yaml v4's built-in alias expansion limit. Version 3.3.2 contains a patch for the issue. Weakness: CWE-674 (Uncontrolled Recursion) ## Which versions are affected by CVE-2026-33320? 5 open source packages ship an affected version, including github.com/tomwright/dasel/v3, github.com/tomwright/dasel and github.com/tomwright/dasel/v2. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `github.com/tomwright/dasel/v3` | Go | From 3.0.0 | 3.3.2 | | `github.com/tomwright/dasel/v3` | Go | From 3.0.0 | 3.3.2 | | `github.com/tomwright/dasel/v3` | Go | From 3.0.0 | 3.3.2 | | `github.com/tomwright/dasel` | Go | All versions | None | | `github.com/tomwright/dasel/v2` | Go | All versions | None | Products: Tomwright Dasel. ## How do I fix CVE-2026-33320? Upgrade github.com/tomwright/dasel/v3 to 3.3.2 or later. ## Is CVE-2026-33320 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33320 exists. Public exploit code: - Hardened dasel v3.3.1 package and image built via Melange and apko. Patching CVE-2026-33320. (github_poc): https://github.com/nedlir/dasel-hardened-container - dasel v3.3.1 packaged with Melange and shipped as a minimal apko image, patched for CVE-2026-33320 (github_poc): https://github.com/rotavori/dasel-melange-apko - Junior Backend Candidate Exercise: Packaging the dasel CLI (v3.3.1) with Melange, fixing CVE-2026-33320, and building a minimal container image using Apko. (github_poc): https://github.com/GonSarrabia/Minimus-Junior-Backend-Exercise ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-33320 and fix it if it is affected. What it is: CVE-2026-33320 is a medium-severity denial of service vulnerability in TomWright dasel, published on 24 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33320 exists. Affected packages and fixed versions: - github.com/tomwright/dasel/v3 (Go): affected from 3.0.0; fixed in 3.3.2 - github.com/tomwright/dasel/v3 (Go): affected from 3.0.0; fixed in 3.3.2 - github.com/tomwright/dasel/v3 (Go): affected from 3.0.0; fixed in 3.3.2 - github.com/tomwright/dasel (Go): affected all versions; no fix listed - github.com/tomwright/dasel/v2 (Go): affected all versions; no fix listed 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-2026-33320/ (Markdown: https://insights.sbomify.com/CVE-2026-33320/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33320 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33320 - OSV: https://osv.dev/vulnerability/CVE-2026-33320 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-33320/ Summaries are generated and may contain mistakes; the official description above is the record.