# CVE-2026-23991: go-tuf affected by client DoS via malformed server response > A compromised TUF repository can cause a denial of service in go-tuf clients by sending malformed metadata that triggers a panic before signature validation. - **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 22 Jan 2026 - **Updated:** 22 Jan 2026 - **Also known as:** AZL-75186, BELL-CVE-2026-23991, CLEANSTART-2026-HN41905, CLEANSTART-2026-JT87240, DEBIAN-CVE-2026-23991, GHSA-846p-jg2w-w324, GO-2026-4348, MINI-26c5-jcfv-9rrq, MINI-26wr-jqrq-5hh3, MINI-274m-48g4-j6v6, MINI-2jqm-9484-fhwj, MINI-2p8q-r2xv-9hx2, MINI-4pq7-x526-89fg, MINI-4v3q-phqf-gr2w, MINI-4wj8-f3q4-94x3, MINI-5wj6-p26m-h8c5, MINI-62qw-pqr7-3cj9, MINI-7c9j-jq68-4mf8, MINI-7q6q-fpxh-3f7h, MINI-85q8-8m34-hv3c, MINI-8h92-gpcg-8j4j, MINI-8jfx-r2rh-2gxx, MINI-8m9f-rq4f-cpgc, MINI-c69f-6rc6-6599, MINI-ccmf-j8qx-3xgg, MINI-cp7w-mjpv-2xxx, MINI-f2pr-wc8g-83p9, MINI-f676-96g2-rxq9, MINI-hjrp-ww3c-cqwj, MINI-j2rw-8whr-mvgq, MINI-jpxx-4h74-jhfv, MINI-mw53-j3fm-pg64, MINI-q8ff-7xj4-xmvf, MINI-qj86-7rv3-p92q, MINI-qp9w-mcp4-394m, MINI-rgwh-px29-7mfj, MINI-v3pq-h3c7-jx7x, MINI-vprc-h95p-vj8q, MINI-wr7v-hh2x-m556, MINI-x5jp-64jq-r5x5, UBUNTU-CVE-2026-23991 ## What is CVE-2026-23991? CVE-2026-23991 is a medium-severity denial of service vulnerability in theupdateframework go-tuf, published on 22 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description go-tuf is a Go implementation of The Update Framework (TUF). Starting in version 2.0.0 and prior to version 2.3.1, if the TUF repository (or any of its mirrors) returns invalid TUF metadata JSON (valid JSON but not well formed TUF metadata), the client will panic during parsing, causing a denial of service. The panic happens before any signature is validated. This means that a compromised repository/mirror/cache can DoS clients without having access to any signing key. Version 2.3.1 fixes the issue. No known workarounds are available. Weakness: CWE-754 (Improper Check for Unusual or Exceptional Conditions), CWE-617 (Reachable Assertion) ## Which versions are affected by CVE-2026-23991? 3 open source packages ship an affected version, including github.com/theupdateframework/go-tuf/v2. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `github.com/theupdateframework/go-tuf/v2` | Go | All versions | 2.3.1 | | `github.com/theupdateframework/go-tuf/v2` | Go | All versions | 2.3.1 | | `github.com/theupdateframework/go-tuf/v2` | Go | All versions | 2.3.1 | Products: Theupdateframework Go-Tuf. ## How do I fix CVE-2026-23991? Upgrade github.com/theupdateframework/go-tuf/v2 to 2.3.1 or later. ## Is CVE-2026-23991 being exploited? There is no known exploitation of CVE-2026-23991 in the wild and no public exploit code. ## Other vulnerabilities in theupdateframework go-tuf - [CVE-2022-29173](https://insights.sbomify.com/CVE-2022-29173/): No protection against rollback attacks in go-tuf (high 8.0) - [CVE-2026-23992](https://insights.sbomify.com/CVE-2026-23992/): go-tuf improperly validates the configured threshold for delegations (medium 5.9) - [CVE-2026-24686](https://insights.sbomify.com/CVE-2026-24686/): go-tuf Path Traversal in TAP 4 Multirepo Client Allows Arbitrary File Write via Malicious Repository Names (medium 4.7) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-23991 and fix it if it is affected. What it is: CVE-2026-23991 is a medium-severity denial of service vulnerability in theupdateframework go-tuf, published on 22 Jan 2026. 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-2026-23991 in the wild and no public exploit code. Affected packages and fixed versions: - github.com/theupdateframework/go-tuf/v2 (Go): affected all versions; fixed in 2.3.1 - github.com/theupdateframework/go-tuf/v2 (Go): affected all versions; fixed in 2.3.1 - github.com/theupdateframework/go-tuf/v2 (Go): affected all versions; fixed in 2.3.1 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-2026-23991/ (Markdown: https://insights.sbomify.com/CVE-2026-23991/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23991 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23991 - OSV: https://osv.dev/vulnerability/CVE-2026-23991 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-23991/ Summaries are generated and may contain mistakes; the official description above is the record.