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.
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
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| pyasn1 · Debian 12.15 (bookworm) | 0.4.8-3+deb12u3 | DEBIAN-CVE-2026-59884 | Jul 31, 2026 |
| pyasn1 · Debian 13.5 (trixie) | 0.6.1-1+deb13u3 | DEBIAN-CVE-2026-59884 | Jul 31, 2026 |
| pyasn1 · Debian 14 | 0.6.4-1 | DEBIAN-CVE-2026-59884 | Jul 31, 2026 |
| pypy-pyasn1 · Ubuntu 22.04.1 LTS (jammy) | 0.4.8-1ubuntu0.3 | pypy-pyasn1 0.4.8-1ubuntu0.3 | Jul 14, 2026 |
| python-pyasn1 · opensuse-leap 16.0 | 0.6.1-160000.5.1 | OPENSUSE-SU-2026:21392-1 | Jul 20, 2026 |
| python-pyasn1 · sles 15.6 | 0.5.0-150400.12.16.1 | SUSE-SU-2026:3238-1 | Jul 24, 2026 |
| python-pyasn1 · sles 15.7 | 0.5.0-150400.12.16.1 | SUSE-SU-2026:3238-1 | Jul 24, 2026 |
| python-pyasn1 · sles 16.0 | 0.6.1-160000.5.1 | SUSE-SU-2026:22830-1 | Jul 20, 2026 |
| python-pyasn1-doc · amzn 2023 | 0.4.8-4.amzn2023.0.5 | ALAS2023-2026-2000 | Aug 3, 2026 |
| python3-pyasn1 · Ubuntu 22.04.1 LTS (jammy) | 0.4.8-1ubuntu0.3 | python3-pyasn1 0.4.8-1ubuntu0.3 | Jul 14, 2026 |
| python3-pyasn1 · Ubuntu 24.04.5 LTS (noble) | 0.4.8-4ubuntu0.3 | python3-pyasn1 0.4.8-4ubuntu0.3 | Jul 14, 2026 |
| python3-pyasn1 · Ubuntu 26.04.1 LTS (resolute) | 0.6.3-1ubuntu0.1 | python3-pyasn1 0.6.3-1ubuntu0.1 | Jul 14, 2026 |
| python3-pyasn1 · amzn 2023 | 0.4.8-4.amzn2023.0.5 | ALAS2023-2026-2000 | Aug 3, 2026 |
| python3-pyasn1-modules · amzn 2023 | 0.4.8-4.amzn2023.0.5 | ALAS2023-2026-2000 | Aug 3, 2026 |
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