# CVE-2026-59884: pyasn1 BER/CER/DER decoder denial of service via unbounded long-form tag IDs

CVE-2026-59884 is fixed in 6 products on 1 platform, first by pypy-pyasn1 0.4.8-1ubuntu0.3, released July 14, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-59884
- Priority: High
- CVSS: 7.5 (Important)
- EPSS: 0.0062
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 14, 2026
- Weakness: Uncontrolled Resource Consumption
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-59884

## Description

pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the BER decoder shared by the CER and DER codecs parses long-form tags by accumulating continuation octets without an upper bound on the tag ID size, allowing a crafted input to force construction of an arbitrarily large integer with CPU cost growing quadratically and to trigger unhandled ValueError exceptions in Python 3.11+ error formatting paths. Any application decoding untrusted BER, CER, or DER input is affected. This issue is fixed in version 0.6.4.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | pyasn1 Debian 12.15 (bookworm) | 0.4.8-3+deb12u3 | [DEBIAN-CVE-2026-59884](https://patchblox.com/security/data/fix/linux/debian-cve-2026-59884.md) | Jul 31, 2026 |
| Linux | pyasn1 Debian 13.5 (trixie) | 0.6.1-1+deb13u3 | [DEBIAN-CVE-2026-59884](https://patchblox.com/security/data/fix/linux/debian-cve-2026-59884.md) | Jul 31, 2026 |
| Linux | pyasn1 Debian 14 | 0.6.4-1 | [DEBIAN-CVE-2026-59884](https://patchblox.com/security/data/fix/linux/debian-cve-2026-59884.md) | Jul 31, 2026 |
| Linux | pypy-pyasn1 Ubuntu 22.04.1 LTS (jammy) | 0.4.8-1ubuntu0.3 | [pypy-pyasn1 0.4.8-1ubuntu0.3](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-pypy-pyasn1-0.4.8-1ubuntu0.3.md) | Jul 14, 2026 |
| Linux | python-pyasn1 opensuse-leap 16.0 | 0.6.1-160000.5.1 | [OPENSUSE-SU-2026:21392-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21392-1.md) | Jul 20, 2026 |
| Linux | python-pyasn1 sles 15.6 | 0.5.0-150400.12.16.1 | [SUSE-SU-2026:3238-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-3238-1.md) | Jul 24, 2026 |
| Linux | python-pyasn1 sles 15.7 | 0.5.0-150400.12.16.1 | [SUSE-SU-2026:3238-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-3238-1.md) | Jul 24, 2026 |
| Linux | python-pyasn1 sles 16.0 | 0.6.1-160000.5.1 | [SUSE-SU-2026:22830-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-22830-1.md) | Jul 20, 2026 |
| Linux | python-pyasn1-doc amzn 2023 | 0.4.8-4.amzn2023.0.5 | [ALAS2023-2026-2000](https://patchblox.com/security/data/fix/linux/alas2023-2026-2000.md) | Aug 3, 2026 |
| Linux | python3-pyasn1 Ubuntu 22.04.1 LTS (jammy) | 0.4.8-1ubuntu0.3 | [python3-pyasn1 0.4.8-1ubuntu0.3](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-python3-pyasn1-0.4.8-1ubuntu0.3.md) | Jul 14, 2026 |
| Linux | python3-pyasn1 Ubuntu 24.04.5 LTS (noble) | 0.4.8-4ubuntu0.3 | [python3-pyasn1 0.4.8-4ubuntu0.3](https://patchblox.com/security/data/fix/linux/ubuntu-noble-python3-pyasn1-0.4.8-4ubuntu0.3.md) | Jul 14, 2026 |
| Linux | python3-pyasn1 Ubuntu 26.04.1 LTS (resolute) | 0.6.3-1ubuntu0.1 | [python3-pyasn1 0.6.3-1ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-python3-pyasn1-0.6.3-1ubuntu0.1.md) | Jul 14, 2026 |
| Linux | python3-pyasn1 amzn 2023 | 0.4.8-4.amzn2023.0.5 | [ALAS2023-2026-2000](https://patchblox.com/security/data/fix/linux/alas2023-2026-2000.md) | Aug 3, 2026 |
| Linux | python3-pyasn1-modules amzn 2023 | 0.4.8-4.amzn2023.0.5 | [ALAS2023-2026-2000](https://patchblox.com/security/data/fix/linux/alas2023-2026-2000.md) | Aug 3, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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