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Vulnerabilities

Vulnerability · CVE-2026-27459

pyOpenSSL is a Python wrapper around the OpenSSL library.

Published Mar 18, 2026 · catalog updated Sep 10, 2026 · pyOpenSSL is a Python

Check if you run it

No confirmed exploitation is on record for CVE-2026-27459. EPSS is 0.92%. Act only if a listed version of pyOpenSSL is a Python is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (pyOpenSSL is a Python).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.2
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.92%
Remediation
Advisory link
Affected products
cpe pyopenssl/pyopenssl

pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 22.0.0 and prior to version 26.0.0, if a user provided callback to returned a cookie value greater than 256 bytes, pyOpenSSL would overflow an OpenSSL provided buffer. Starting in version 26.0.0, cookie values that are too long are now rejected.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe pyopenssl/pyopensslversion unspecified

How to fix CVE-2026-27459

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-27459. EPSS is 0.92%. Act only if a listed version of pyOpenSSL is a Python is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-120: Classic Buffer Overflow. EPSS 0.92%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 18, 2026 · NIST NVD

    Detected

    pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 22.0.0 and prior to version 26.0.0, if a user provided callback to returned a cookie value greater than 256 bytes, pyOpenSSL would overflow an OpenSSL provided buffer. Starting in version 26.0.0, cookie values that are too long are now rejected.

  2. Sep 10, 2026 · NIST NVD

    Updated

    pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 22.0.0 and prior to version 26.0.0, if a user provided callback to returned a cookie value greater than 256 bytes, pyOpenSSL would overflow an OpenSSL provided buffer. Starting in version 26.0.0, cookie values that are too long are now rejected.

Sources

  • CVE.orgVulnerability recordCVE-2026-27459

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-27459

    30-day exploitation probability 0.9%

    first.org
  • NIST NVDVulnerability recordCVE-2026-27459

    pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 22.0.0 and prior to version 26.0.0, if a user provided callback to returned a cookie value greater than 256 bytes, pyOpenSSL would overflow an OpenSSL provided buffer. Sta

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.