pyasn1 <=0.6.2 DoS via uncontrolled ASN.1 recursion
CVE-2026-30922 Published on March 18, 2026

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.

NVD

Vulnerability Analysis

CVE-2026-30922 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. An automatable proof of concept (POC) exploit exists. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
NONE
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
NONE
Integrity Impact:
NONE
Availability Impact:
HIGH

Weakness Type

What is a Stack Exhaustion Vulnerability?

The product does not properly control the amount of recursion which takes place, consuming excessive resources, such as allocated memory or the program stack.

CVE-2026-30922 has been classified to as a Stack Exhaustion vulnerability or weakness.


Products Associated with CVE-2026-30922

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Canonical Ubuntu Linux
 

Affected Versions

pyasn1 Version < 0.6.3 is affected by CVE-2026-30922

Exploit Probability

EPSS
0.05%
Percentile
15.37%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.