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Erlang\/otpApplication · Erlang

CVE-2026-55953

HIGH · 7.4 CVSS v3.1 Developing Published 2026-07-27
Fix available
A fix is available. Upgrade to 11.2.12.11 / 11.6.0.4 or later.
See remediation →
83/100
Remediation priority · High
Remotely reachable No privileges Zero-click 3 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The Erlang/OTP ssl TLS 1.2 (and earlier) and DTLS client does not verify that the cipher suite selected by the server in ServerHello was among the suites offered by the client in ClientHello. The client-side tls_handshake:hello/5 handler validates the negotiated protocol version and the downgrade sentinel but hands the server-chosen suite directly to ssl_handshake:handle_server_hello_extensions/9, which installs it without a membership check. The TLS 1.3 client path performs this check (per RFC 8446), so it is not affected. An on-path attacker between the client and the intended server can respond with a ServerHello selecting an anonymous key exchange suite such as TLS_DH_anon_* or TLS_ECDH_anon_* that the client never offered. Anonymous suites do not require the server to present a certificate, so the entire verify_peer and cacerts configuration is bypassed: the attacker completes the handshake with its own ephemeral parameters, no certificate is validated, no hostname is checked, and ssl:connect returns {ok, Socket}. All subsequent application traffic is readable and modifiable by the attacker. This issue affects OTP from OTP R13B03 before OTP 27.3.4.15, from OTP 28.0 before OTP 28.5.0.4, and from OTP 29.0 before OTP 29.0.4, corresponding to ssl from 3.10.7 before 11.2.12.11, from 11.3 before 11.6.0.4, and from 11.7 before 11.7.4. Whether OTP before OTP R13B03, corresponding to ssl before 3.10.7, is affected is unknown.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · low confidence
Developing — this CVE was published recently and its authoritative NVD entry is still being established, so we're holding a technical summary until the source data settles rather than publish something unreliable. Re-checking after 2026-08-10.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Erlang\/otpApplication
Affected:>= 17.0, < 27.3.4.15>= 28.0, < 28.5.0.4>= 29.0, < 29.0.4
Erlang\/sslApplication
Affected:>= 5.3.4, < 11.2.12.11>= 11.3, < 11.6.0.4>= 11.7, < 11.7.4

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 11.2.12.11 / 11.6.0.4 / 11.7.4 or later
Fixed in 11.2.12.1111.6.0.411.7.4
Recommended fix High confidence

OTP 27.3.4.15+ (ssl 11.2.12.11+), OTP 28.5.0.4+ (ssl 11.6.0.4+), or OTP 29.0.4+ (ssl 11.7.4+)

  1. 1. Identify the current OTP version in use by running 'erl -eval 'erlang:display(erlang:system_info(otp_release)), halt().' -noshell'
  2. 2. Determine which OTP major version branch you are on (OTP 27, 28, or 29)
  3. 3. For OTP 27.x users: Upgrade to OTP 27.3.4.15 or later (ssl 11.2.12.11 or later)
  4. 4. For OTP 28.x users: Upgrade to OTP 28.5.0.4 or later (ssl 11.6.0.4 or later)
  5. 5. For OTP 29.x users: Upgrade to OTP 29.0.4 or later (ssl 11.7.4 or later)
  6. 6. After upgrading, verify the ssl application version matches the fixed version: in an Erlang shell, run 'application:version(ssl)'
  7. 7. Test TLS/DTLS connections to ensure handshakes complete successfully with proper certificate validation

Generated from the published advisory — verify against the referenced sources before acting.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

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Peer-ranked notes from engineers who’ve handled CVE-2026-55953 in production — separate from our analysis above.

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