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pyOpenSSL 26.0.0 was released with fixes for two security vulnerabilities tracked as CVE-2026-27459 and CVE-2026-27448. The first issue is a buffer overflow in DTLS handling that can occur when a cookie callback returns a value longer than DTLS1_COOKIE_LENGTH bytes. The second affects Context.set_tlsext_servername_callback, where exceptions raised by the callback were previously swallowed and the TLS handshake continued as though the callback had completed successfully.
The vulnerabilities were disclosed through the oss-security mailing list and corresponding GitHub security advisories, with dark_haxor credited for reporting CVE-2026-27459 and Leury Castillo credited for reporting CVE-2026-27448. In follow-up discussion, pyOpenSSL maintainer Alex Gaynor said both issues require misbehaving Python code and are therefore unlikely to be exploitable, but the defects were nonetheless corrected in the new release.
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In a follow-up discussion published on 2026-03-20, Alex Gaynor said both vulnerabilities require misbehaving Python code and were therefore unlikely to be exploitable in his opinion. This added impact assessment to the initial release announcement.
On 2026-03-20, pyOpenSSL 26.0.0 was released to fix two security issues: a buffer overflow when a DTLS cookie callback returns an oversized cookie, and improper handling of exceptions in Context.set_tlsext_servername_callback. The release was accompanied by changelog references and GitHub security advisories for both CVEs.
The pyOpenSSL project credited dark_haxor with reporting CVE-2026-27459, a DTLS cookie callback buffer overflow, and Leury Castillo with reporting CVE-2026-27448, an issue where exceptions in a server name callback were silently swallowed and the TLS handshake continued. The exact reporting dates were not provided in the references.
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OpenSSL released versions **1.0.1u** and **1.0.2i** to correct multiple vulnerabilities affecting earlier releases. The flaws include DTLS denial-of-service issues: `CVE-2016-2181`, which lets an attacker advance a connection’s replay-protection window with an unauthenticated future-epoch record and cause valid packets to be discarded, and `CVE-2016-2179`, which can retain unnecessary out-of-order handshake fragments and consume roughly 1.5 MB of memory per DTLS connection. `CVE-2016-6302` can also crash servers using a custom SHA-512 TLS session-ticket HMAC callback through an integer underflow and out-of-bounds read. The updates additionally address memory-safety defects in certificate and utility processing. `CVE-2016-2182` is an out-of-bounds write in `BN_bn2dec()` caused by unchecked `BN_div_word()` failures when handling oversized BIGNUM values, while `CVE-2016-2180` can cause an out-of-bounds read when the `openssl ts` utility parses crafted time-stamp data containing large OIDs. `CVE-2016-6306` involves a small out-of-bounds read in certificate-message handling when client authentication is enabled. Red Hat issued fixes for affected RHEL 6 and 7 packages, including RHSA-2016:1940, with later JBoss Core Services updates for `CVE-2016-2182`.
Aug 28, 2026
OpenSSL disclosed a broad set of vulnerabilities affecting ASN.1 parsing, PKCS#12, CMS/PKCS#7, QUIC, OCSP, CMP/CRMF, DH key validation, AEAD cipher handling, and certificate and email validation across the 4.0, 3.6, 3.5, 3.4, and 3.0 branches. The most severe issue, **CVE-2026-45447**, is a high-severity heap use-after-free in `PKCS7_verify()` that can be triggered by specially crafted PKCS#7 or S/MIME signed messages and could lead to crashes, heap corruption, or potentially remote code execution. The advisory also details moderate-severity flaws that could enable forged CMS `AuthEnvelopedData` messages, denial-of-service conditions in QUIC and OCSP processing, a TLS client double-free via OCSP stapling, a QUIC server `NULL` dereference, and cryptographic failures in AES-OCB when applications use the `EVP_Cipher()` one-shot API, alongside numerous lower-severity parsing, validation, and bounds-checking bugs. OpenSSL said most issues were fixed in **4.0.1**, **3.6.3**, **3.5.7**, **3.4.6**, and **3.0.21**, with **1.1.1zh** and **1.0.2zq** issued for supported legacy customers; most flaws were reported as outside the OpenSSL FIPS module boundary, except **CVE-2026-42770**, which affects FIPS modules in multiple supported branches.
Jun 29, 2026
Two high-severity denial-of-service vulnerabilities in Erlang/OTP's **`ssl`** application allow unauthenticated remote attackers to disrupt secure listeners before authentication completes. **`CVE-2026-55950`** affects the DTLS **`dtls_packet_demux`** component, where a time-of-check/time-of-use race condition can be triggered by rapidly sending multiple DTLS `ClientHello` messages from the same source IP address and port. Because the demultiplexing process is shared across DTLS associations on a listener, a successful crash terminates **all active DTLS sessions** on that listener rather than only the attacker's connection. A second flaw, **`CVE-2026-55952`**, affects **TLS 1.3** servers when malformed `ClientHello` pre-shared key data causes session ticket handling to crash after the software fails to validate that PSK identity and binder lists are the same length. A single crafted request can make TLS 1.3 unusable on an affected listener until the **`ssl`** application is restarted, while TLS 1.2 is not affected. Erlang/OTP maintainers released fixes in **OTP `29.0.3`**, **`28.5.0.3`**, and **`27.3.4.14`**; the DTLS issue was addressed in a GitHub commit that changed logic in **`dtls_packet_demux.erl`** to safely handle existing keys during connection state transitions.
Jul 12, 2026