{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-23943", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-01-19T14:23:14.343Z", "datePublished": "2026-03-13T09:11:57.794Z", "dateUpdated": "2026-03-13T09:11:57.794Z"}, "containers": {"cna": {"affected": [{"cpes": ["cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*"], "defaultStatus": "unknown", "modules": ["ssh_transport"], "packageName": "ssh", "packageURL": "pkg:otp/ssh?repository_url=https:%2F%2Fgithub.com%2Ferlang%2Fotp&vcs_url=git%20https:%2F%2Fgithub.com%2Ferlang%2Fotp.git", "product": "OTP", "programFiles": ["src/ssh_transport.erl"], "programRoutines": [{"name": "ssh_transport:decompress/2"}, {"name": "ssh_transport:handle_packet_part/4"}], "repo": "https://github.com/erlang/otp", "vendor": "Erlang", "versions": [{"changes": [{"at": "5.5.1", "status": "unaffected"}, {"at": "5.2.11.6", "status": "unaffected"}, {"at": "5.1.4.14", "status": "unaffected"}], "lessThan": "*", "status": "affected", "version": "3.0.1", "versionType": "otp"}, {"changes": [{"at": "pkg:otp/ssh@5.5.1", "status": "unaffected"}, {"at": "pkg:otp/ssh@5.2.11.6", "status": "unaffected"}, {"at": "pkg:otp/ssh@5.1.4.14", "status": "unaffected"}], "lessThan": "pkg:otp/ssh@*", "status": "affected", "version": "pkg:otp/ssh@3.0.1", "versionType": "purl"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:erlang:erlang\\/otp:*:*:*:*:*:*:*:*"], "defaultStatus": "unknown", "modules": ["ssh_transport"], "packageName": "erlang/otp", "packageURL": "pkg:github/erlang/otp", "product": "OTP", "programFiles": ["lib/ssh/src/ssh_transport.erl"], "programRoutines": [{"name": "ssh_transport:decompress/2"}, {"name": "ssh_transport:handle_packet_part/4"}], "repo": "https://github.com/erlang/otp", "vendor": "Erlang", "versions": [{"changes": [{"at": "28.4.1", "status": "unaffected"}, {"at": "27.3.4.9", "status": "unaffected"}, {"at": "26.2.5.18", "status": "unaffected"}], "lessThan": "*", "status": "affected", "version": "17.0", "versionType": "otp"}, {"changes": [{"at": "43a87b949bdff12d629a8c34146711d9da93b1b1", "status": "unaffected"}, {"at": "93073c3bd338c60cd2bae715ce6a1d4ffc1a8fd3", "status": "unaffected"}, {"at": "0c1c04b191f6ab940e8fcfabce39eb5a8a6440a4", "status": "unaffected"}], "lessThan": "*", "status": "affected", "version": "07b8f441ca711f9812fad9e9115bab3c3aa92f79", "versionType": "git"}]}], "credits": [{"lang": "en", "type": "reporter", "value": "Igor Morgenstern / Aisle Research"}, {"lang": "en", "type": "remediation developer", "value": "Micha\u0142 W\u0105sowski"}, {"lang": "en", "type": "remediation reviewer", "value": "Jakub Witczak"}], "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "Improper Handling of Highly Compressed Data (Compression Bomb) vulnerability in Erlang OTP ssh (ssh_transport modules) allows Denial of Service via Resource Depletion.<p>The SSH transport layer advertises legacy zlib compression by default and inflates attacker-controlled payloads pre-authentication without any size limit, enabling reliable memory exhaustion DoS.</p><p>Two compression algorithms are affected:</p><ul><li><b>zlib:</b> Activates immediately after key exchange, enabling unauthenticated attacks</li><li><b>zlib@openssh.com:</b> Activates post-authentication, enabling authenticated attacks</li></ul><p>Each SSH packet can decompress ~255 MB from 256 KB of wire data (1029:1 amplification ratio). Multiple packets can rapidly exhaust available memory, causing OOM kills in memory-constrained environments.</p><p>This vulnerability is associated with program files <tt>lib/ssh/src/ssh_transport.erl</tt> and program routines <tt>ssh_transport:decompress/2</tt>, <tt>ssh_transport:handle_packet_part/4</tt>.</p><p>This issue affects OTP from OTP 17.0 until OTP 28.4.1, 27.3.4.9 and 26.2.5.18 corresponding to ssh from 3.0.1 until 5.5.1, 5.2.11.6 and 5.1.4.14.</p>"}], "value": "Improper Handling of Highly Compressed Data (Compression Bomb) vulnerability in Erlang OTP ssh (ssh_transport modules) allows Denial of Service via Resource Depletion.\n\nThe SSH transport layer advertises legacy zlib compression by default and inflates attacker-controlled payloads pre-authentication without any size limit, enabling reliable memory exhaustion DoS.\n\nTwo compression algorithms are affected:\n\n* zlib: Activates immediately after key exchange, enabling unauthenticated attacks\n* zlib@openssh.com: Activates post-authentication, enabling authenticated attacks\n\nEach SSH packet can decompress ~255 MB from 256 KB of wire data (1029:1 amplification ratio). Multiple packets can rapidly exhaust available memory, causing OOM kills in memory-constrained environments.\n\nThis vulnerability is associated with program files lib/ssh/src/ssh_transport.erl and program routines ssh_transport:decompress/2, ssh_transport:handle_packet_part/4.\n\nThis issue affects OTP from OTP 17.0 until OTP 28.4.1, 27.3.4.9 and 26.2.5.18 corresponding to ssh from 3.0.1 until 5.5.1, 5.2.11.6 and 5.1.4.14."}], "impacts": [{"capecId": "CAPEC-130", "descriptions": [{"lang": "en", "value": "CAPEC-130 Excessive Allocation"}]}, {"capecId": "CAPEC-490", "descriptions": [{"lang": "en", "value": "CAPEC-490 Amplification"}]}], "metrics": [{"cvssV4_0": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "baseScore": 6.9, "baseSeverity": "MEDIUM", "exploitMaturity": "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:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N", "version": "4.0", "vulnAvailabilityImpact": "LOW", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-409", "description": "CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-03-13T09:11:57.794Z"}, "references": [{"tags": ["vendor-advisory"], "url": "https://github.com/erlang/otp/security/advisories/GHSA-c836-qprm-jw9r"}, {"tags": ["x_version-scheme"], "url": "https://www.erlang.org/doc/system/versions.html#order-of-versions"}, {"tags": ["patch"], "url": "https://github.com/erlang/otp/commit/43a87b949bdff12d629a8c34146711d9da93b1b1"}, {"tags": ["patch"], "url": "https://github.com/erlang/otp/commit/93073c3bd338c60cd2bae715ce6a1d4ffc1a8fd3"}, {"tags": ["patch"], "url": "https://github.com/erlang/otp/commit/0c1c04b191f6ab940e8fcfabce39eb5a8a6440a4"}], "source": {"discovery": "EXTERNAL"}, "title": "Pre-auth SSH DoS via unbounded zlib inflate", "workarounds": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p><b>Best workaround - Disable all compression:</b></p><pre>{preferred_algorithms, [{compression, ['none']}]}</pre><p><b>Alternative mitigations (less secure):</b></p><ul><li>Disable only pre-auth zlib compression (authenticated users can still exploit via zlib@openssh.com):<pre>{modify_algorithms, [{rm, [{compression, ['zlib']}]}]}</pre></li><li>Limit concurrent sessions (reduces attack surface but does not prevent exploitation):<pre>{max_sessions, N} % Cap total concurrent sessions (default is infinity)</pre></li></ul>"}], "value": "Best workaround - Disable all compression:\n\n{preferred_algorithms, [{compression, ['none']}]}\n\nAlternative mitigations (less secure):\n\n* Disable only pre-auth zlib compression (authenticated users can still exploit via zlib@openssh.com):\n {modify_algorithms, [{rm, [{compression, ['zlib']}]}]}\n* Limit concurrent sessions (reduces attack surface but does not prevent exploitation):\n {max_sessions, N} % Cap total concurrent sessions (default is infinity)"}], "x_generator": {"engine": "Vulnogram 0.2.0"}}}}

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