FKIE_CVE-2026-55953
Vulnerability from fkie_nvd - Published: 2026-07-27 16:17 - Updated: 2026-08-03 22:16
Severity
Summary
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.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"cpes": [
"cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"tls_handshake",
"ssl_handshake",
"ssl"
],
"packageName": "otp",
"packageURL": "pkg:sid/erlang.org/otp",
"product": "OTP",
"programFiles": [
"lib/ssl/src/tls_handshake.erl",
"lib/ssl/src/ssl_handshake.erl",
"lib/ssl/src/ssl.erl"
],
"programRoutines": [
{
"name": "tls_handshake:hello/5"
},
{
"name": "ssl_handshake:handle_server_hello_extensions/9"
},
{
"name": "ssl:connect/2"
},
{
"name": "ssl:connect/3"
},
{
"name": "ssl:connect/4"
}
],
"vendor": "Erlang",
"versions": [
{
"lessThan": "R13B03",
"status": "unknown",
"version": "0",
"versionType": "otp"
},
{
"lessThan": "27.3.4.15",
"status": "affected",
"version": "R13B03",
"versionType": "otp"
},
{
"lessThan": "28.5.0.4",
"status": "affected",
"version": "28.0",
"versionType": "otp"
},
{
"lessThan": "29.0.4",
"status": "affected",
"version": "29.0",
"versionType": "otp"
}
]
},
{
"cpes": [
"cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"tls_handshake",
"ssl_handshake",
"ssl"
],
"packageName": "ssl",
"packageURL": "pkg:otp/ssl?repository_url=https:%2F%2Fgithub.com%2Ferlang%2Fotp\u0026vcs_url=git%20https:%2F%2Fgithub.com%2Ferlang%2Fotp.git",
"product": "OTP",
"programFiles": [
"src/tls_handshake.erl",
"src/ssl_handshake.erl",
"src/ssl.erl"
],
"programRoutines": [
{
"name": "tls_handshake:hello/5"
},
{
"name": "ssl_handshake:handle_server_hello_extensions/9"
},
{
"name": "ssl:connect/2"
},
{
"name": "ssl:connect/3"
},
{
"name": "ssl:connect/4"
}
],
"repo": "https://github.com/erlang/otp",
"vendor": "Erlang",
"versions": [
{
"lessThan": "3.10.7",
"status": "unknown",
"version": "0",
"versionType": "otp"
},
{
"lessThan": "11.2.12.11",
"status": "affected",
"version": "3.10.7",
"versionType": "otp"
},
{
"lessThan": "11.6.0.4",
"status": "affected",
"version": "11.3",
"versionType": "otp"
},
{
"lessThan": "11.7.4",
"status": "affected",
"version": "11.7",
"versionType": "otp"
}
]
},
{
"collectionURL": "https://github.com",
"cpes": [
"cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"tls_handshake",
"ssl_handshake",
"ssl"
],
"packageName": "erlang/otp",
"packageURL": "pkg:github/erlang/otp",
"product": "OTP",
"programFiles": [
"lib/ssl/src/tls_handshake.erl",
"lib/ssl/src/ssl_handshake.erl",
"lib/ssl/src/ssl.erl"
],
"programRoutines": [
{
"name": "tls_handshake:hello/5"
},
{
"name": "ssl_handshake:handle_server_hello_extensions/9"
},
{
"name": "ssl:connect/2"
},
{
"name": "ssl:connect/3"
},
{
"name": "ssl:connect/4"
}
],
"repo": "https://github.com/erlang/otp",
"vendor": "Erlang",
"versions": [
{
"changes": [
{
"at": "064e236414614f9085cbbbd6eacf0e43c02d1b4b",
"status": "unaffected"
},
{
"at": "0a82596d425abe43dc2e0b3d74aa1557ef74051c",
"status": "unaffected"
},
{
"at": "e6ff938116b2872bccc478af7fefb56627285b77",
"status": "unaffected"
}
],
"lessThan": "*",
"status": "affected",
"version": "84adefa331c4159d432d22840663c38f155cd4c1",
"versionType": "git"
}
]
}
],
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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.\n\nAn 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.\n\nThis issue affects OTP from OTP\u00a0R13B03 before OTP\u00a027.3.4.15, from OTP\u00a028.0 before OTP\u00a028.5.0.4, and from OTP\u00a029.0 before OTP\u00a029.0.4, 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\u00a0R13B03, corresponding to ssl before 3.10.7, is affected is unknown."
}
],
"id": "CVE-2026-55953",
"lastModified": "2026-08-03T22:16:50.353",
"metrics": {
"cvssMetricV40": [
{
"cvssData": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"availabilityRequirement": "NOT_DEFINED",
"baseScore": 9.1,
"baseSeverity": "CRITICAL",
"confidentialityRequirement": "NOT_DEFINED",
"exploitMaturity": "NOT_DEFINED",
"integrityRequirement": "NOT_DEFINED",
"modifiedAttackComplexity": "NOT_DEFINED",
"modifiedAttackRequirements": "NOT_DEFINED",
"modifiedAttackVector": "NOT_DEFINED",
"modifiedPrivilegesRequired": "NOT_DEFINED",
"modifiedSubAvailabilityImpact": "NOT_DEFINED",
"modifiedSubConfidentialityImpact": "NOT_DEFINED",
"modifiedSubIntegrityImpact": "NOT_DEFINED",
"modifiedUserInteraction": "NOT_DEFINED",
"modifiedVulnAvailabilityImpact": "NOT_DEFINED",
"modifiedVulnConfidentialityImpact": "NOT_DEFINED",
"modifiedVulnIntegrityImpact": "NOT_DEFINED",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "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/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",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "HIGH",
"vulnIntegrityImpact": "HIGH",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-55953",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-07-27T18:33:59.966358Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-07-27T16:17:49.500",
"references": [
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://cna.erlef.org/cves/CVE-2026-55953.html"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/erlang/otp/commit/064e236414614f9085cbbbd6eacf0e43c02d1b4b"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/erlang/otp/commit/0a82596d425abe43dc2e0b3d74aa1557ef74051c"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/erlang/otp/commit/e6ff938116b2872bccc478af7fefb56627285b77"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://github.com/erlang/otp/security/advisories/GHSA-c6cw-pr89-w882"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://osv.dev/vulnerability/EEF-CVE-2026-55953"
},
{
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"url": "https://www.erlang.org/doc/system/versions.html#order-of-versions"
}
],
"sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-757"
}
],
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"type": "Secondary"
}
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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