Inefficient Algorithmic Complexity Affecting pyasn1 package, versions [,0.6.5)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PYTHON-PYASN1-22113909
- published1 Nov 2026
- disclosed30 Oct 2026
- creditmanus-use
Introduced: 30 Oct 2026
NewCVE-2026-119197 (opens in a new tab)How to fix?
Upgrade pyasn1 to version 0.6.5 or higher.
Overview
Affected versions of this package are vulnerable to Inefficient Algorithmic Complexity in the RealPayloadDecoder.valueDecoder method in pyasn1/codec/ber/decoder.py. An attacker can hold a decoder on one CPU core for seconds or longer by supplying a binary-encoded ASN.1 REAL with a large mantissa, which the method accumulates one octet at a time in a shift-and-slice loop whose cost grows quadratically in the mantissa length. Exploitation requires only that a REAL value reach a BER, CER, or DER decoder, with or without an asn1Spec, and the work occurs inside decode() even when the application never uses the resulting object.
Workaround
This vulnerability can be avoided by rejecting or strictly limiting the size of attacker-controlled ASN.1 input before passing it to the decoder, with the limit set against the application's available CPU time and request volume.