CVE-2026-27459 describes a critical buffer overflow vulnerability (CVSS 9.8) affecting pyOpenSSL versions 22.0.0 through 25.x.x. This flaw occurs when a user-provided callback to `set_cookie_generate_callback` returns a cookie value exceeding 256 bytes, causing an OpenSSL buffer to overflow. The vulnerability is network-exploitable with low attack complexity and no user interaction, potentially leading to complete compromise of confidentiality, integrity, and availability. While the FAUCET Risk Score is 45.0/100, there is currently no evidence of active exploitation, public exploit code, or significant community discussion.
| Vendor | Product | Version(s) | CPE |
|---|---|---|---|
>= 22.0.0, < 26.0.0CPE matchmatch criteria | cpe:2.3:a:pyopenssl:pyopenssl:*:*:*:*:*:*:*:* |
CVSS version used by this source: 4.0
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.
The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.