# CVE-2026-27459: pyOpenSSL DTLS cookie callback buffer overflow CVE-2026-27459 is fixed in 51 products on 1 platform, first by DEBIAN-CVE-2026-27459, released March 18, 2026. It is not reported as exploited. Patch Radar priority: High. - Web page: https://patchblox.com/security/cve/CVE-2026-27459 - Priority: High - CVSS: 9.8 (Important) - EPSS: 0.0075 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Mar 17, 2026 - Weakness: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-27459 ## Description 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. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | kryoptic Fedora 43 | 1.5.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | kryoptic-debuginfo Fedora 43 | 1.5.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | kryoptic-debugsource Fedora 43 | 1.5.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | kryoptic-tools Fedora 43 | 1.5.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | kryoptic-tools-debuginfo Fedora 43 | 1.5.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | pyOpenSSL Fedora 43 | 26.0.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | pyOpenSSL-doc Fedora 43 | 26.0.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | pyopenssl Debian 13.5 (trixie) | 25.0.0-1+deb13u1 | [DEBIAN-CVE-2026-27459](https://patchblox.com/security/data/fix/linux/debian-cve-2026-27459.md) | Mar 18, 2026 | | Linux | pyopenssl Debian 14 | 26.0.0-1 | [DEBIAN-CVE-2026-27459](https://patchblox.com/security/data/fix/linux/debian-cve-2026-27459.md) | Mar 18, 2026 | | Linux | python-cryptography Fedora 43 | 46.0.5-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | python-cryptography-debugsource Fedora 43 | 46.0.5-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | python-pyOpenSSL opensuse-leap 15.6 | 23.2.0-150400.3.13.1 | [SUSE-SU-2026:1192-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-1192-1.md) | Apr 7, 2026 | | Linux | python-pyOpenSSL opensuse-leap 16.0 | 25.0.0-160000.3.1 | [OPENSUSE-SU-2026:20419-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-20419-1.md) | Mar 25, 2026 | | Linux | python-pyOpenSSL sles 15.6 | 23.2.0-150400.3.13.1 | [SUSE-SU-2026:1192-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-1192-1.md) | Apr 7, 2026 | | Linux | python-pyOpenSSL sles 15.7 | 23.2.0-150400.3.13.1 | [SUSE-SU-2026:1192-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-1192-1.md) | Apr 7, 2026 | | Linux | python-pyOpenSSL sles 16.0 | 25.0.0-160000.3.1 | [SUSE-SU-2026:20930-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-20930-1.md) | Mar 25, 2026 | | Linux | python3-cryptography Fedora 43 | 46.0.5-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | python3-cryptography-debuginfo Fedora 43 | 46.0.5-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | python3-openssl Ubuntu 24.04.5 LTS (noble) | 23.2.0-1ubuntu0.1 | [python3-openssl 23.2.0-1ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-python3-openssl-23.2.0-1ubuntu0.1.md) | Apr 15, 2026 | | Linux | python3-openssl Ubuntu 25.10 (questing) | 25.0.0-1ubuntu0.1 | [python3-openssl 25.0.0-1ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-questing-python3-openssl-25.0.0-1ubuntu0.1.md) | Apr 15, 2026 | | Linux | python3-pyOpenSSL Fedora 43 | 26.0.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-asn1 Fedora 43 | 0.22.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-asn1+default-devel Fedora 43 | 0.22.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-asn1+std-devel Fedora 43 | 0.22.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-asn1-devel Fedora 43 | 0.22.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-asn1_derive Fedora 43 | 0.22.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-asn1_derive+default-devel Fedora 43 | 0.22.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-asn1_derive-devel Fedora 43 | 0.22.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-cryptoki Fedora 43 | 0.12.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-cryptoki+default-devel Fedora 43 | 0.12.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-cryptoki+generate-bindings-devel Fedora 43 | 0.12.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-cryptoki+serde-devel Fedora 43 | 0.12.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-cryptoki-devel Fedora 43 | 0.12.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-cryptoki-sys Fedora 43 | 0.5.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-cryptoki-sys+bindgen-devel Fedora 43 | 0.5.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-cryptoki-sys+default-devel Fedora 43 | 0.5.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-cryptoki-sys+generate-bindings-devel Fedora 43 | 0.5.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-cryptoki-sys-devel Fedora 43 | 0.5.0-2.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+aead-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+cipher-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+default-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+dsa-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+ec-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+ecdh-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+ecdsa-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+eddsa-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+fpe-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+hkdf-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+keywrap-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+mac-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+num-bigint-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+primality-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+rsa_enc-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+rsa_sig-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof+xdh-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | | Linux | rust-wycheproof-devel Fedora 43 | 0.6.0-1.fc43 | [FEDORA-2026-9D5B9F45EC](https://patchblox.com/security/data/fix/linux/fedora-2026-9d5b9f45ec.md) | Mar 19, 2026 | --- Data as of 2026-11-08T13:06:02Z UTC. 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