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CVE-2026-55953— TLS 1.2 and DTLS client accepts unoffered anonymous cipher suite, bypassing server authentication

Quick assessment

Affected
Erlang OTP
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Erlang OTP是瑞典Erlang社区的一套构建分布式系统的中间件平台。 Erlang OTP 17.0版本至29.0.4版本之前版本、28.5.0.4版本之前版本和27.3.4.15版本之前版本存在加密问题漏洞，该漏洞源于客户端在TLS握手过程中未验证服务器选择的密码套件是否属于客户端提供的套件，导致中间人攻击者可以利用匿名密钥交换套件，绕过证书验证和主机名检查，从而能够读取和修改应用流量。

CVSS 9.1 · Critical EPSS 0.23% · P14

Possible ATT&CK Techniques 1 AI

T1557 · Adversary-in-the-Middle

Affected Version Matrix 9

VendorProduct Version RangeStatus
Erlang OTP < 17.0 unknown
17.0< 27.3.4.15 affected
28.0< 28.5.0.4 affected
29.0< 29.0.4 affected
< 5.3.4 unknown
5.3.4< 11.2.12.11 affected
11.3< 11.6.0.4 affected
11.7< 11.7.4 affected
… +1 more rows
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I. Basic Information for CVE-2026-55953

Vulnerability Information
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Vulnerability Title
TLS 1.2 and DTLS client accepts unoffered anonymous cipher suite, bypassing server authentication
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
在会话协商时选择低安全性的算法(算法降级)
Source: CVE Program / CVE List V5
Vulnerability Title
Erlang OTP 加密问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Erlang OTP是瑞典Erlang社区的一套构建分布式系统的中间件平台。 Erlang OTP 17.0版本至29.0.4版本之前版本、28.5.0.4版本之前版本和27.3.4.15版本之前版本存在加密问题漏洞，该漏洞源于客户端在TLS握手过程中未验证服务器选择的密码套件是否属于客户端提供的套件，导致中间人攻击者可以利用匿名密钥交换套件，绕过证书验证和主机名检查，从而能够读取和修改应用流量。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Erlang OTP 17.0 ~ 27.3.4.15 cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
Erlang OTP 5.3.4 ~ 11.2.12.11 cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
Erlang OTP 84adefa331c4159d432d22840663c38f155cd4c1 ~ * cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-55953

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III. Intelligence Information for CVE-2026-55953

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Patches & Fixes for CVE-2026-55953 (3)

Vendor Advisories for CVE-2026-55953 (3)

Same Patch Batch · Erlang · 2026-07-27 · 8 CVEs total

CVE-2026-58227 8.7 HIGH TLS/DTLS denial of service via unbounded recursion on cross-signed peer certificate chain
CVE-2026-59251 8.7 HIGH Denial of service via exponential certificate policy tree growth in path validation
CVE-2026-59250 8.3 HIGH Megaco flex scanner buffer overflow via oversized property parm name
CVE-2026-54890 8.2 HIGH BEAM VM crash via integer underflow in binary_to_term BIT_BINARY_EXT decoding
CVE-2026-42792 6.3 MEDIUM epmd permanent DoS via EMFILE on accept(2) in erts
CVE-2026-55737 5.1 MEDIUM Heap pointer corruption via signed/unsigned mismatch in LARGE_TUPLE_EXT decoding in erts e
CVE-2026-47078 4.8 MEDIUM Relative path traversal in zip:unzip/zip:extract via check_dir_level depth-counter bypass

IV. Related Vulnerabilities

Same product: OTP
Same vendor: Erlang
Same weakness: CWE-757