CVE-2026-55953
published 2026-07-27CVE-2026-55953: 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…
PriorityP348high7.4CVSS 3.1
AVNACHPRNUINSUCHIHAN
EPSS
0.23%
14.1th percentile
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 17.0 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 5.3.4 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 17.0, corresponding to ssl before 5.3.4, is affected is unknown.
Affected
15 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | erlang | — | — |
| erlang | erlang_otp | >= 17.0 < 27.3.4.15 | 27.3.4.15 |
| erlang | erlang_otp | >= 28.0 < 28.5.0.4 | 28.5.0.4 |
| erlang | erlang_otp | >= 29.0 < 29.0.4 | 29.0.4 |
| erlang | erlang_ssl | >= 11.3 < 11.6.0.4 | 11.6.0.4 |
| erlang | erlang_ssl | >= 11.7 < 11.7.4 | 11.7.4 |
| erlang | erlang_ssl | >= 5.3.4 < 11.2.12.11 | 11.2.12.11 |
| erlang | otp | >= 11.3 < 11.6.0.4 | 11.6.0.4 |
| erlang | otp | >= 11.7 < 11.7.4 | 11.7.4 |
| erlang | otp | >= 17.0 < 27.3.4.15 | 27.3.4.15 |
| erlang | otp | >= 28.0 < 28.5.0.4 | 28.5.0.4 |
| erlang | otp | >= 29.0 < 29.0.4 | 29.0.4 |
| erlang | otp | >= 5.3.4 < 11.2.12.11 | 11.2.12.11 |
| erlang | otp | >= 84adefa331c4159d432d22840663c38f155cd4c1 < * | * |
| ubuntu | erlang | — | — |
CVSS provenance
nvdv3.17.4HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
nvdv4.09.1CRITICALCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vendor_redhat9.1CRITICAL
vendor_ubuntu7.5HIGH
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Ubuntu
Erlang vulnerabilities
vendor_ubuntu·2026-09-28·CVSS 7.5
CVE-2026-23941 [HIGH] Erlang vulnerabilities
Title: Erlang vulnerabilities
Summary: Several security issues were fixed in Erlang.
It was discovered that the Erlang Port Mapper Daemon did not properly
handle slow connections. A remote attacker could possibly use this issue
to cause a denial of service. (CVE-2026-42792)
It was discovered that Erlang incorrectly handled certain external term
format data, leading to heap corruption. An attacker could possibly use
this issue to cause Erlang to crash, resulting in a denial of service.
This issue only affected Ubuntu 24.04 LTS and Ubuntu 26.04 LTS.
(CVE-2026-55737)
It was discovered that Erlang incorrectly handled invalid external term
format data. An attacker could possibly use this issue to cause Erlang to
crash, resulting in a denial of service. This issue only affected Ubuntu
26.04
Red Hat
erlang/otp: Erlang/OTP ssl client: Authentication bypass via unoffered anonymous cipher suite acceptance
vendor_redhat·2026-07-27·CVSS 9.1
CVE-2026-55953 [CRITICAL] CWE-940 erlang/otp: Erlang/OTP ssl client: Authentication bypass via unoffered anonymous cipher suite acceptance
erlang/otp: Erlang/OTP ssl client: Authentication bypass via unoffered anonymous cipher suite acceptance
A flaw was found in the Erlang/OTP ssl client. This vulnerability allows an on-path attacker to bypass server authentication in TLS 1.2 (and earlier) and DTLS connections. By tricking the client into accepting an unoffered anonymous cipher suite, the attacker can complete the handshake without a valid server certificate. This enables the attacker to read and modify all subsequent application traffic, leading to significant information disclosure and integrity compromise.
Statement: Red Hat rates this flaw as Important (CVSS 7.4), lower than the CVE description alone might suggest, because successful exploitation requires an on-path (man-in-the-middle) attacker positioned between the a
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2026-55953 erlang: Erlang/OTP ssl client: Authentication bypass via unoffered anonymous cipher suite acceptance [epel-all]
bugzilla·2026-07-30·CVSS 9.1
CVE-2026-55953 [CRITICAL] CVE-2026-55953 erlang: Erlang/OTP ssl client: Authentication bypass via unoffered anonymous cipher suite acceptance [epel-all]
CVE-2026-55953 erlang: Erlang/OTP ssl client: Authentication bypass via unoffered anonymous cipher suite acceptance [epel-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
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.
Bugzilla
CVE-2026-55953 erlang: Erlang/OTP ssl client: Authentication bypass via unoffered anonymous cipher suite acceptance [fedora-all]
bugzilla·2026-07-30·CVSS 9.1
CVE-2026-55953 [CRITICAL] CVE-2026-55953 erlang: Erlang/OTP ssl client: Authentication bypass via unoffered anonymous cipher suite acceptance [fedora-all]
CVE-2026-55953 erlang: Erlang/OTP ssl client: Authentication bypass via unoffered anonymous cipher suite acceptance [fedora-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
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
Bugzilla
CVE-2026-55953 erlang/otp: Erlang/OTP ssl client: Authentication bypass via unoffered anonymous cipher suite acceptance
bugzilla·2026-07-27·CVSS 9.1
CVE-2026-55953 [CRITICAL] CVE-2026-55953 erlang/otp: Erlang/OTP ssl client: Authentication bypass via unoffered anonymous cipher suite acceptance
CVE-2026-55953 erlang/otp: Erlang/OTP ssl client: Authentication bypass via unoffered anonymous cipher suite acceptance
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_
https://cna.erlef.org/cves/CVE-2026-55953.htmlhttps://github.com/erlang/otp/commit/064e236414614f9085cbbbd6eacf0e43c02d1b4bhttps://github.com/erlang/otp/commit/0a82596d425abe43dc2e0b3d74aa1557ef74051chttps://github.com/erlang/otp/commit/e6ff938116b2872bccc478af7fefb56627285b77https://github.com/erlang/otp/security/advisories/GHSA-c6cw-pr89-w882https://osv.dev/vulnerability/EEF-CVE-2026-55953https://www.erlang.org/doc/system/versions.html#order-of-versions
2026-07-27
Published