CVE-2026-30922
pyasn1 Vulnerable to Denial of Service via Unbounded Recursion
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.
- Affected
- pyasn1
- CVSS v3.1 CNA
- 7.5 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - CVSS v3.0 GitHub
- 7.5 HIGH
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - EPSS
- 0.97% chance of exploitation in the next 30 days, 61st percentile
- Published
- 2026-03-18
- Updated
- 2026-09-17
Proof-of-concept exploits (1)
Security advisories
- pyasn1/pyasn1/security/advisories/GHSA-jr27-m4p2-rc6r
- pyasn1/pyasn1/commit/25ad481c19fdb006e20485ef3fc2e5b3eff30ef0