Answer in brief
CVE-2026-27459 records a Critical severity (CVSS 9.8) vulnerability in pyOpenSSL DTLS cookie callback buffer overflow. The current sources do not mark it as known exploited. The current feed maps pyca/pyopenssl (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
Answer in brief
CVE-2026-27459 records a Critical severity (CVSS 9.8) vulnerability in pyOpenSSL DTLS cookie callback buffer overflow. The current sources do not mark it as known exploited. The current feed maps pyca/pyopenssl (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps pyca/pyopenssl (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| pyca/pyopensslgeneric | >= 22.0.0, < 26.0.0 | Not reported |
Published upstream
Mar 17, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 3, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 1, 2026
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 `set_cookie_generate_callback` 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.
Quoted source text, attributed separately from HOL analysis.
CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps pyca/pyopenssl (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| pyca/pyopensslgeneric | >= 22.0.0, < 26.0.0 | Not reported |
Published upstream
Mar 17, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 3, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jul 1, 2026
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 `set_cookie_generate_callback` 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.
Quoted source text, attributed separately from HOL analysis.