Operating system, libraries and runtimes

OpenSSL DTLS handshake retransmission read (CVE-2026-84782)

OpenSSL check

OpenSSL's security release of 29 September 2026 fixed 14 flaws. One is rated High: CVE-2026-84782, "DTLS retransmits handshake messages from a stale buffer offset". When DTLS retransmits a handshake message it can read from the wrong place in a buffer, so a remote peer may receive unintended plaintext heap memory in the handshake data, or the program may crash. CISA scored it 8.2 (confidentiality low, availability high). It was found by Laurent Gaffie of Secorizon, with the fix by Ryan Hooper. The FIPS module is not affected.

Who is actually exposed

Software that speaks DTLS: VPN servers such as ocserv, VoIP and WebRTC servers such as Asterisk, FreeSWITCH, Janus and coturn, and IoT endpoints. Ordinary TLS (HTTPS, SMTP, IMAP, databases) does not use the vulnerable code. Node.js and Python's ssl module have no DTLS API. A host with an affected OpenSSL and no DTLS service has little practical exposure, but the library should still be updated.

How the script decides

It also reports running DTLS-capable daemons from a short list, and processes that still hold a replaced OpenSSL in memory, because a library update does not reach a running process until it restarts. LibreSSL is not OpenSSL and is not affected. Node.js's bundled OpenSSL is reported for information.

Quick start

curl -fLO https://raw.githubusercontent.com/PrivacySafe/security-patches/refs/heads/main/openssl/openssl-check.sh
less openssl-check.sh
chmod +x openssl-check.sh
./openssl-check.sh check

Commands

Env: OPENSSL_BIN, OPENSSL_PKG_VERSION, OPENSSL_OS_RELEASE, OPENSSL_CHANGELOG, OPENSSL_PROC and OPENSSL_NODE override the openssl command, the package version, /etc/os-release, a changelog file (plain or .gz), /proc and the node command. OPENSSL_NO_PACKAGE=1 treats the installed openssl as not owned by a package.

Update

Update the OpenSSL package, then restart the services that use it (needrestart, or a reboot). For 3.0, 1.1.1 and 1.0.2 without a vendor backport, the public fix does not exist: move to a supported branch (3.4 or later) or use a distribution package that carries the fix.

Sources

• OpenSSL vulnerabilities page
• Ubuntu: CVE-2026-84782
• The Hacker News: OpenSSL fixes a high-severity DTLS flaw

Before you run it

• The fix. Update the OpenSSL package, then restart the services that use it (needrestart or a reboot). Fixed public releases are 4.0.3, 3.6.5, 3.5.9 and 3.4.8. For 3.0, 1.1.1 and 1.0.2 the fix is available only to premium-support customers, and 3.1 to 3.3 are end of life.
• A distribution build is judged by its package. Ubuntu's fixed builds (26.04: 3.5.5-1ubuntu3.6, 24.04: 3.0.13-0ubuntu3.16, 22.04: 3.0.2-0ubuntu1.30) and the package changelog naming the CVE come first. The upstream version is used only for a build that is not from a package. For other distributions the script points you to your distribution's advisory.
• The flaw is only reachable through DTLS. Ordinary TLS services do not use the vulnerable code, and Node.js has no DTLS API. The script lists the DTLS-capable services it finds running and processes still holding a replaced OpenSSL in memory.
• It also reads running containers. With SCAN_CONTAINERS=1 (the default) it asks each running docker and podman container for its own distribution, package and openssl version, and judges it by the container's rules, not the host's. OpenSSL linked statically into a program, inside or outside a container, is not visible. Copies bundled under /opt, /usr/local, /srv and /home are listed, and whoever ships that software updates them. There is no hunt.

Red Hat advisories

Red Hat's advisory list (security advisories released 2026-04-01 to 2026-11-03) names the CVEs below. A Red Hat build is judged by its RPM release, not by the upstream version number, because Red Hat backports fixes: the advisory names the release that fixes it. A CVE with no advisory in the list has none for that period, which is not the same as not affected. The current state is on Red Hat's CVE database.

Other packages that bundle OpenSSL carry the same CVE; they are counted, not listed.

• CVE-2026-84782: 31 advisories, 2026-08-17 to 2026-10-29; 25 important, 5 critical, 1 moderate; by stream, RHEL 8 3, RHEL 9 5, RHEL 10 1, Hummingbird 7, container image 15; most often openssl (5), compat-openssl11 (4), satellite/iop-host-inventory-rhel9 (2), satellite/iop-vmaas-rhel9 (2). All of them: Red Hat's CVE page.

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