# CVE-2026-57585: MessagePack: Out-of-bounds read/crash on Unpacker reuse after caught error > Attackers can cause a crash via out-of-bounds read when reusing the Unpacker after an error, leading to denial of service. - **Severity:** High 7.5 (`CVSS:3.1/AV:N/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:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 30 Jun 2026 - **Updated:** 1 Jul 2026 - **Also known as:** AZL-91746, BELL-CVE-2026-57585, CLEANSTART-2026-FV21331, CLEANSTART-2026-KD93591, CLEANSTART-2026-KG31017, CLEANSTART-2026-MV63007, CLEANSTART-2026-OD76726, CLEANSTART-2026-PW41000, CLEANSTART-2026-QQ77815, CLEANSTART-2026-RR86072, CLEANSTART-2026-TI03982, CLEANSTART-2026-VQ21617, CLEANSTART-2026-ZD80119, DEBIAN-CVE-2026-57585, ECHO-7ab8-b488-83cb, GHSA-6v7p-g79w-8964, MINI-22w8-qgg5-7m99, MINI-2wcm-q7pv-x2wq, MINI-33gp-r3jq-j7gh, MINI-c2v6-c37f-c9f9, MINI-f4vq-2r4q-qqc6, MINI-f5vw-fxrm-26jj, MINI-g4q2-f22g-6whv, MINI-hcr4-mxpq-456q, MINI-p8w6-prwj-h9vp, MINI-pg8q-mv99-jg6h, MINI-pp3q-q4gx-75q8, MINI-q6p9-xmf8-8g57, MINI-rjqq-wvvh-wv8q, MINI-v4f8-wh37-692r, MINI-vc24-2g78-grx6, MINI-vjqr-9c5m-g9g2, MINI-vr56-g93v-7crc, MINI-xjf9-244c-9px7, PYSEC-2026-3625, ROOT-APP-PYPI-GHSA-6v7p-g79w-8964, SUSE-SU-2026:22704-1, SUSE-SU-2026:23169-1, SUSE-SU-2026:3113-1, SUSE-SU-2026:3297-1, SUSE-SU-2026:3932-1, SUSE-SU-2026:4443-1, UBUNTU-CVE-2026-57585, openSUSE-SU-2026:11586-1, openSUSE-SU-2026:21239-1 ## What is CVE-2026-57585? CVE-2026-57585 is a high-severity use after free vulnerability in msgpack-python, published on 30 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description MessagePack is the serializer implementation for Python msgpack.org. Prior to 1.2.1, there is an Out-of-bounds read/crash on Unpacker reuse after a caught error, potentially leading to a DoS attack. If the Unpacker is used repeatedly after an error occurs, the process may crash with a SEGV. This issue has been fixed in version 1.2.1. Weakness: CWE-416 (Use After Free) ## Which versions are affected by CVE-2026-57585? 3 open source packages ship an affected version, including msgpack. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `msgpack` | PyPI | All versions | 1.2.1 | | `msgpack` | PyPI | All versions | 1.2.1 | | `msgpack` | PyPI | All versions | 1.2.1 | | `python-msgpack` | SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | All versions | 1.0.7-150400.10.9.1 | | `python-msgpack` | SUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS | All versions | 1.0.7-150400.10.9.1 | | `python-msgpack` | SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | All versions | 1.0.7-150400.10.9.1 | | `python-msgpack` | SUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS | All versions | 1.0.7-150400.10.9.1 | | `python-msgpack` | SUSE:Linux Enterprise Micro 5.3 | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise Micro 5.4 | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise Micro 5.5 | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise Module for Public Cloud 15 SP7 | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise Module for Python 3 15 SP7 | All versions | 1.0.7-150600.3.5.1 | | `python-msgpack` | SUSE:Linux Enterprise Server 15 SP4-LTSS | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise Server 15 SP4-LTSS | All versions | 1.0.7-150400.10.9.1 | | `python-msgpack` | SUSE:Linux Enterprise Server 15 SP5-LTSS | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise Server 15 SP5-LTSS | All versions | 1.0.7-150400.10.9.1 | | `python-msgpack` | SUSE:Linux Enterprise Server 15 SP6-LTSS | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise Server 15 SP6-LTSS | All versions | 1.0.7-150600.3.5.1 | | `python-msgpack` | SUSE:Linux Enterprise Server for SAP Applications 15 SP4 | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise Server for SAP Applications 15 SP4 | All versions | 1.0.7-150400.10.9.1 | | `python-msgpack` | SUSE:Linux Enterprise Server for SAP Applications 15 SP5 | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise Server for SAP Applications 15 SP5 | All versions | 1.0.7-150400.10.9.1 | | `python-msgpack` | SUSE:Linux Enterprise Server for SAP Applications 15 SP6 | All versions | 0.5.6-150100.3.6.1 | | `python-msgpack` | SUSE:Linux Enterprise Server for SAP Applications 15 SP6 | All versions | 1.0.7-150600.3.5.1 | | `python-msgpack` | SUSE:Linux Micro 6.0 | All versions | 1.0.5-2.1 | | `python-msgpack` | SUSE:Linux Micro 6.1 | All versions | 1.0.5-slfo.1.1_2.1 | | `python-msgpack-python` | SUSE:Manager Client Tools 12 | All versions | 0.4.6-8.8.1 | | `python-msgpack` | openSUSE:Leap 16.0 | All versions | 1.1.0-160000.3.1 | | `python-msgpack` | openSUSE:Tumbleweed | All versions | 1.2.1-1.1 | Products: Msgpack Messagepack. ## How do I fix CVE-2026-57585? Upgrade msgpack to 1.2.1 or later. ## Is CVE-2026-57585 being exploited? There is no known exploitation of CVE-2026-57585 in the wild and no public exploit code. ## Other vulnerabilities in msgpack-python - [CVE-2026-21452](https://insights.sbomify.com/CVE-2026-21452/): MessagePack for Java Vulnerable to Remote DoS via Malicious EXT Payload Allocation (high 7.5) - [CVE-2026-54522](https://insights.sbomify.com/CVE-2026-54522/): MessagePack::Buffer#clear Use-After-Free that Enables Cross-Buffer Disclosure (low 2.1) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-57585 and fix it if it is affected. What it is: CVE-2026-57585 is a high-severity use after free vulnerability in msgpack-python, published on 30 Jun 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-2026-57585 in the wild and no public exploit code. Affected packages and fixed versions: - msgpack (PyPI): affected all versions; fixed in 1.2.1 - msgpack (PyPI): affected all versions; fixed in 1.2.1 - msgpack (PyPI): affected all versions; fixed in 1.2.1 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-2026-57585/ (Markdown: https://insights.sbomify.com/CVE-2026-57585/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-57585 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-57585 - OSV: https://osv.dev/vulnerability/CVE-2026-57585 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-57585/ Summaries are generated and may contain mistakes; the official description above is the record.