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Pyasn1Application

CVE-2026-59886

HIGH · 7.5 CVSS v3.1 Published 2026-07-14
Fix available
A fix is available. Upgrade to 0.6.4 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click Patch available 5 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the univ.Real type converted its mantissa, base, and exponent value to a Python float using exact big-integer exponentiation. A BER, CER, or DER encoded REAL value only a few bytes long can carry a very large exponent, causing float conversion through prettyPrint(), str(), comparison, arithmetic, int(), or an explicit float() call to consume excessive CPU and memory and hang applications that decode untrusted ASN.1 data and then print, log, or compare decoded objects. This issue is fixed in version 0.6.4.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The pyasn1 library's univ.Real type contains a Denial of Service vulnerability where BER, CER, or DER encoded REAL values with large exponents cause excessive CPU and memory consumption during float conversion. When decoded ASN.1 data containing maliciously large exponents is processed through prettyPrint(), str(), comparison, arithmetic, int(), or float() calls, the exact big-integer exponentiation can hang the application.

MitigationUpgrade pyasn1 to version 0.6.4 or later. If upgrade is not immediately possible, validate and limit the exponent size of decoded REAL values before performing any conversion operations.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Pyasn1Application
Affected:< 0.6.4

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify pyasn1 installation and version
    Run 'pip show pyasn1' or check your dependency lock file to determine the installed version of pyasn1
    Affected if The installed version is lower than 0.6.4
  2. Confirm use of univ.Real type in code
    Search your codebase for imports or usage of 'pyasn1.univ.Real' or 'from pyasn1.type import univ' followed by Real() instantiation
    Affected if Your code directly uses or processes univ.Real objects from pyasn1
  3. Check for ASN.1 decoded data handling
    Review code that decodes BER, CER, or DER encoded data, particularly any ASN.1 REAL type values being processed
    Affected if Your application decodes ASN.1 data containing REAL values from untrusted or external sources
  4. Identify vulnerable conversion operations
    Search for calls to prettyPrint(), str(), int(), float() on Real objects, or any arithmetic/comparison operations involving Real values
    Affected if Any decoded Real values are passed to these conversion methods or used in comparisons/arithmetic
  5. Verify external data source exposure
    Determine if ASN.1 data comes from external/network sources that could contain maliciously crafted large exponents
    Affected if Real values are decoded from untrusted or network-accessible ASN.1 data sources

You are affected if pyasn1 version is below 0.6.4 AND your code decodes ASN.1 REAL values from external sources AND uses conversion operations (prettyPrint, str, int, float) or arithmetic/comparison on those Real objects.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 0.6.4 or later
Fixed in 0.6.4
Vendor patch github.com →
Interim mitigation

Upgrade pyasn1 to version 0.6.4 or later. If upgrade is not immediately possible, validate and limit the exponent size of decoded REAL values before performing any conversion operations.

Recommended fix High confidence

0.6.4

  1. Check the current pyasn1 version installed: pip show pyasn1 or grep pyasn1 requirements.txt/pipfile
  2. Upgrade to version 0.6.4 or later: pip install pyasn1>=0.6.4
  3. Verify the upgrade was successful: pip show pyasn1 and confirm version >= 0.6.4
  4. Test that ASN.1 decoding functionality works correctly with the updated library

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Pyasn1 Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing8.0 h
  • Review / QA3.0 h
17.0 hours of engineering $2,900
Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-59886 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data