Breaks TLS verification in Erlang/OTP runtime used by many server products (e.g., RabbitMQ), enabling broad on‑path MITM and data exposure.
CVE-2026-55953
Erlang/OTP TLS client accepts attacker-chosen anonymous ciphers, enabling MITM.
Is CVE-2026-55953 being exploited?
Not confirmed. CVE-2026-55953 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.23% probability of exploitation in the next 30 days.
How severe is CVE-2026-55953?
CVE-2026-55953 is rated Critical with a CVSS score of 9.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-55953?
Yes. A fix has been recorded for CVE-2026-55953. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-55953 affect?
CVE-2026-55953 affects Erlang/OTP 17.0 through pre-fixed releases, Fixed in OTP 27.3.4.15, 28.5.0.4, 29.0.4, Applications using Erlang TLS (e.g., RabbitMQ, CouchDB, EMQX). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-55953?
Upgrade to the patched OTP releases or apply vendor updates immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
On‑path attacker can force anonymous key exchange, bypass cert/hostname checks, and read/modify TLS traffic (full MITM).
Immediate action required
- affected< 17.0
- affected>= 17.0 and < 27.3.4.15
- affected>= 28.0 and < 28.5.0.4
- affected>= 29.0 and < 29.0.4
- affected< 5.3.4
- affected>= 5.3.4 and < 11.2.12.11
- affected>= 11.3 and < 11.6.0.4
- affected>= 11.7 and < 11.7.4
- affected>= 84adefa331c4159d432d22840663c38f155cd4c1 and < *
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.