OpenSSL released fixes for CVE-2026-84782, a high-severity DTLS handshake retransmission flaw that can allow a connected peer to disclose adjacent heap memory in plaintext or crash an affected application. The out-of-bounds read occurs when retransmission starts while transmission of a fragmented handshake message is suspended, leaving OpenSSL with an incorrect buffer position. CISA assigned the issue a CVSS score of 8.2; no exploitation was known as of September 29, 2026, and OpenSSL has published no workaround.
Organizations should update to OpenSSL 4.0.3, 3.6.5, 3.5.9, or 3.4.8, or install their vendor’s corrected package. The flaw also affects 3.0, 1.1.1, and 1.0.2, but patches for those older branches require premium support. OpenSSL 3.0 reached public end of life on September 7, 2026 and no longer receives publicly available security fixes, increasing upgrade urgency; OpenSSL recommends moving to the 3.5 LTS release, supported through April 2030, or OpenSSL 4.0. The vulnerable DTLS logic lies outside the FIPS module boundary.

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19 events from the most recent confirmed update back to the earliest known activity.
SUSE released advisory SUSE-SU-2026:4419-1 with OpenSSL 3 package updates for SLES 15 and SLES for SAP 15, addressing CVE-2026-35189, CVE-2026-54872, CVE-2026-75805, CVE-2026-75806, CVE-2026-77696, and CVE-2026-84782. The fixes cover memory-allocation, timing side-channel, NULL-pointer dereference, and DTLS denial-of-service and retransmission flaws.
SUSE published security update SUSE-SU-2026:4418-1 addressing CVE-2026-84782 in the openssl-3-livepatches package on SUSE Linux Enterprise Server 15. The prescribed remediation is to update the affected package.
TuxCare published a CentOS 8 security update under advisory CLSA-2026-1790933563 covering CVE-2026-35189 and CVE-2026-84782, rated Important. The Tenable record identifies the patch publication date but does not specify affected packages or fixed package versions.
TuxCare published a CentOS 8.5 security update under advisory CLSA-2026-1790933161 covering CVE-2026-35189 and CVE-2026-84782, rated Important. The Tenable record dates patch publication to October 2, 2026, but does not specify affected packages or fixed package versions.
TuxCare published a CentOS 8.4 security update under advisory CLSA-2026-1790933443 covering CVE-2026-35189 and CVE-2026-84782, rated Important. The Tenable listing records the patch publication but does not specify affected packages or fixed package versions.
The Canadian Centre for Cyber Security published advisory AV26-980 covering multiple OpenSSL vulnerabilities and identifying releases earlier than 1.0.2zs, 1.1.1zj, 3.0.23, 3.4.8, 3.5.9, 3.6.5, and 4.0.3 as affected. It recommended that users review OpenSSL vulnerability information and apply necessary updates as available.
The CVE record explained that a DTLS handshake write suspended with WANT_WRITE could share buffer-position and write-state data with a timer-triggered retransmission, causing an incorrect retransmission offset, heap-memory disclosure, or inconsistent state and process termination. OpenSSL corrected this by resetting the retransmission read position and deferring retransmissions while a handshake write remains suspended.
OpenSSL's September 29 advisory detailed low-severity flaws affecting QUIC, CMP, DTLS, TLS, and EC/SM2 cryptography, including several denial-of-service and timing/cache side-channel issues. It also identified CVE-2026-54873 as a QUIC stream-frame memory-retention flaw and stated that none of the 14 listed vulnerabilities affects the FIPS module boundary.
A vulnerability identified as CVE-2026-54873 was published affecting OpenSSL-related and associated platform packages on CentOS 7 and 8 and RHEL 7 through 10. The notice reported no known exploits and did not provide technical details or remediation guidance.
The September 29 OpenSSL releases also fixed CVE-2026-84783, a moderate-severity flaw that can crash certain multi-threaded TLS clients or servers requesting client certificates, and CVE-2026-75806, a low-severity DTLS 1.2 connection-termination issue.
Ubuntu fixed CVE-2026-84782 in libssl3t64 packages for Ubuntu 26.04 LTS and 24.04 LTS, and in libssl3 for Ubuntu 22.04 LTS. Ubuntu advised users to reboot after installing the updates.
CISA assigned CVE-2026-84782 a CVSS score of 8.2 and recorded no known exploitation at that time.
OpenSSL disclosed CVE-2026-84782, a high-severity DTLS out-of-bounds read that can expose adjacent heap memory to a connected peer or crash the process. It released public fixes in 4.0.3, 3.6.5, 3.5.9, and 3.4.8; fixes for 3.0, 1.1.1, and 1.0.2 were restricted to premium-support customers.
OpenSSL 3.0 reached end of life after its five-year LTS support period and stopped receiving publicly available security fixes. Extended paid support remained available.
Laurent Gaffie of Secorizon reported the DTLS retransmission vulnerability later assigned CVE-2026-84782 to OpenSSL. Ryan Hooper subsequently developed the correction.
OpenSSL released the 3.0 series as a long-term-support version, beginning its five-year public-support period.
The Guyana National CIRT advised users and administrators to review OpenSSL’s September 29 security advisory and apply necessary updates. Its notice identified releases earlier than 1.0.2zs, 1.1.1zj, 3.0.23, 3.4.8, 3.5.9, 3.6.5, and 4.0.3 as affected.
Debian fixed CVE-2026-84782 in Debian 13 through openssl version 3.5.7-1~deb13u3, released as DSA-6531-1. Debian 12 remained listed as vulnerable as of September 30.
OpenSSL security updates addressed 14 vulnerabilities, including four rated high severity, which could enable denial of service or disclosure of sensitive information. The updates cover affected 4.x, 3.6.x, 3.5.x, 3.4.x, 3.0.x, 1.1.x, and 1.0.x releases, with fixed-version thresholds specified for each branch.
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