CVE-2026-59886: pyasn1 resource consumption in univ.Real float conversion

CVE-2026-59886 · Severity: high · CVSS 7.5 · Published 2026-07-14

A vulnerability in the pyasn1 library, which is used to handle data encoded in the ASN.1 format, can allow an attacker to crash an application. By sending a specially crafted data value, an attacker can force the application to consume excessive CPU and memory resources, leading to a denial-of-service. This affects any system that processes and then logs, prints, or compares untrusted ASN.1 data.

Technologies: Pyasn1, pyasn1 (PyPI). Vendors: Pyasn1, PyPI.

Quick answers

Is CVE-2026-59886 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-59886 being exploited in the wild.
How severe is CVE-2026-59886?
High severity, with a CVSS score of 7.5, published 14 July 2026.
Which products and versions are affected?
Pyasn1 < 0.6.4, <= 0.6.3; pyasn1 (PyPI) ECOSYSTEM:introduced=0,fixed=0.6.4.
Is there a fix for CVE-2026-59886?
Yes. pyasn1 (PyPI): upgrade to 0.6.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-59886 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-59886?
Check whether you run Pyasn1 or pyasn1 (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • pyasn1 (PyPI): upgrade to 0.6.4 or later
    pip install "pyasn1>=0.6.4"

Technical details

The pyasn1 library's univ.Real type is vulnerable to uncontrolled resource consumption (CWE-400) during float conversion. The root cause is the use of exact big-integer exponentiation when converting (mantissa, base, exponent) values to Python floats. An attacker can provide a BER/CER/DER-encoded REAL value with a very large exponent, causing the process to hang while attempting to materialize an astronomically large integer. This is triggered by operations such as prettyPrint(), str(), comparisons, or explicit float() calls on decoded objects. The issue is fixed in version 0.6.4 by using math.ldexp() for binary values and implementing overflow checks for decimal values.

Affected products

  • pyasn1 pyasn1 <= 0.6.3

Identifiers

  • CVE-2026-59886
  • GHSA-hm4w-wwcw-mr6r
  • PYSEC-2026-3457

Timeline

  • 2026-07-09: disclosed: Initial report to GitHub Advisory Database
  • 2026-07-14: advisory: NVD publication date
  • 2026-07-21: patched: GitHub Advisory reviewed and updated with patch information

References

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