Amazon Linux 2023 Security Advisory: ALAS2023-2026-1538
Advisory Released Date: 2026-04-13
Advisory Updated Date: 2026-04-13
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.3, the `pyasn1` library is vulnerable to a Denial of Service (DoS) attack caused by uncontrolled recursion when decoding ASN.1 data with deeply nested structures. An attacker can supply a crafted payload containing thousands of nested `SEQUENCE` (`0x30`) or `SET` (`0x31`) tags with "Indefinite Length" (`0x80`) markers. This forces the decoder to recursively call itself until the Python interpreter crashes with a `RecursionError` or consumes all available memory (OOM), crashing the host application. This is a distinct vulnerability from CVE-2026-23490 (which addressed integer overflows in OID decoding). The fix for CVE-2026-23490 (`MAX_OID_ARC_CONTINUATION_OCTETS`) does not mitigate this recursion issue. Version 0.6.3 fixes this specific issue. (CVE-2026-30922)
Affected Packages:
python-pyasn1
Issue Correction:
Run dnf update python-pyasn1 --releasever 2023.11.20260413 or dnf update --advisory ALAS2023-2026-1538 --releasever 2023.11.20260413 to update your system.
More information on how to update your system can be found on this page: Amazon Linux 2023 documentation
noarch:
python3-pyasn1-0.4.8-4.amzn2023.0.4.noarch
python-pyasn1-doc-0.4.8-4.amzn2023.0.4.noarch
python3-pyasn1-modules-0.4.8-4.amzn2023.0.4.noarch
src:
python-pyasn1-0.4.8-4.amzn2023.0.4.src