CVE-2026-68956 (GCVE-0-2026-68956)
Vulnerability from cvelistv5
Published
2026-09-22 08:49
Modified
2026-09-24 20:07
Severity ?
VLAI Severity ?
EPSS score ?
CWE
- CWE-770 - Allocation of Resources Without Limits or Throttling
Summary
Allocation of Resources Without Limits or Throttling vulnerability in Erlang/OTP ssh allows an authenticated remote attacker to exhaust node memory by repeatedly opening session channels that are never assigned a handler.
The "session" clause of ssh_connection:handle_msg/4 checks only minimal_remote_max_packet_size before calling setup_session/5, which unconditionally builds a #channel{} record and stores it in the ETS channel cache. The max_channels daemon option is consulted only by ssh_channel_sup:max_num_channels_not_exceeded/2, which counts supervisor children, so a channel that never gets a shell, exec, or subsystem handler is invisible to the limit and setting the option to a finite value does not mitigate the attack. RFC 4254 section 5.1 permits many session channels per connection, and each record costs only a few hundred bytes, so a single authenticated connection can accumulate channels until the node runs out of memory and the emulator terminates, affecting every application on it. No file contents, credentials, or write access are obtainable.
This issue affects OTP from OTP 18.1.2 before OTP 27.3.4.18, OTP 28.5.0.7, and OTP 29.1.1, corresponding to ssh from 4.1.1 before 5.2.11.13, 5.5.2.6, and 6.0.6. Whether OTP before OTP 18.1.2, corresponding to ssh before 4.1.1, is affected is unknown.
References
Impacted products
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\"ssh_connection:setup_session/5\"}, {\"name\": \"ssh_channel_sup:max_num_channels_not_exceeded/2\"}]}], \"datePublic\": \"2026-09-22T08:49:22.000Z\", \"references\": [{\"url\": \"https://github.com/erlang/otp/security/advisories/GHSA-qhcm-px9c-rvfh\", \"name\": \"GitHub Advisory\", \"tags\": [\"related\", \"vendor-advisory\"]}, {\"url\": \"https://cna.erlef.org/cves/CVE-2026-68956.html\", \"name\": \"EEF CNA record for CVE-2026-68956\", \"tags\": [\"related\"]}, {\"url\": \"https://osv.dev/vulnerability/EEF-CVE-2026-68956\", \"name\": \"OSV record EEF-CVE-2026-68956\", \"tags\": [\"related\"]}, {\"url\": \"https://www.erlang.org/doc/system/versions.html#order-of-versions\", \"name\": \"Erlang/OTP version ordering\", \"tags\": [\"x_version-scheme\"]}, {\"url\": \"https://github.com/erlang/otp/commit/84df3d4d0278e21a36a453bfee94799f0df67c2a\", \"name\": \"Introducing commit 84df3d4 in erlang/otp\", \"tags\": [\"related\"]}, {\"url\": \"https://github.com/erlang/otp/commit/79c2d2be17d902c5f53969b5806b725efda831be\", \"name\": \"Fix commit 79c2d2b in erlang/otp\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/erlang/otp/commit/e18100975f0e5a8d59d02de00df12247a91b443b\", \"name\": \"Fix commit e181009 in erlang/otp\", \"tags\": [\"patch\"]}, {\"url\": \"https://github.com/erlang/otp/commit/e2bbad0107bba41491a4d549686fd023db8740da\", \"name\": \"Fix commit e2bbad0 in erlang/otp\", \"tags\": [\"patch\"]}], \"workarounds\": [{\"lang\": \"en\", \"value\": \"No option bounds the number of idle session channels, so the following reduce exposure without eliminating the issue.\\n\\n* Restrict network access to the SSH daemon to trusted clients. Exploitation requires a successfully authenticated session, so limiting who can authenticate is the most effective control available.\\n* Set the max_sessions daemon option to a finite value to bound the number of concurrent connections. This limits how many connections can mount the attack in parallel, though a single connection still suffices to exhaust memory.\\n* Apply operating-system or firewall connection-rate and connection-count limits per source address.\\n* Monitor node memory externally and restart the emulator when it exceeds a threshold.\\n\\nSetting max_channels is not a workaround: idle session channels bypass that check entirely.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eNo option bounds the number of idle session channels, so the following reduce exposure without eliminating the issue.\u003c/p\u003e\\n\u003cul\u003e\\n\u003cli\u003eRestrict network access to the SSH daemon to trusted clients. Exploitation requires a successfully authenticated session, so limiting who can authenticate is the most effective control available.\u003c/li\u003e\\n\u003cli\u003eSet the \u003ccode\u003emax_sessions\u003c/code\u003e daemon option to a finite value to bound the number of concurrent connections. This limits how many connections can mount the attack in parallel, though a single connection still suffices to exhaust memory.\u003c/li\u003e\\n\u003cli\u003eApply operating-system or firewall connection-rate and connection-count limits per source address.\u003c/li\u003e\\n\u003cli\u003eMonitor node memory externally and restart the emulator when it exceeds a threshold.\u003c/li\u003e\\n\u003c/ul\u003e\\n\u003cp\u003eSetting \u003ccode\u003emax_channels\u003c/code\u003e is not a workaround: idle session channels bypass that check entirely.\u003c/p\u003e\", \"base64\": false}, {\"type\": \"text/markdown\", \"value\": \"No option bounds the number of idle session channels, so the following reduce exposure without eliminating the issue.\\n\\n* Restrict network access to the SSH daemon to trusted clients. Exploitation requires a successfully authenticated session, so limiting who can authenticate is the most effective control available.\\n* Set the `max_sessions` daemon option to a finite value to bound the number of concurrent connections. This limits how many connections can mount the attack in parallel, though a single connection still suffices to exhaust memory.\\n* Apply operating-system or firewall connection-rate and connection-count limits per source address.\\n* Monitor node memory externally and restart the emulator when it exceeds a threshold.\\n\\nSetting `max_channels` is not a workaround: idle session channels bypass that check entirely.\", \"base64\": false}]}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"Allocation of Resources Without Limits or Throttling vulnerability in Erlang/OTP ssh allows an authenticated remote attacker to exhaust node memory by repeatedly opening session channels that are never assigned a handler.\\n\\nThe \\\"session\\\" clause of ssh_connection:handle_msg/4 checks only minimal_remote_max_packet_size before calling setup_session/5, which unconditionally builds a #channel{} record and stores it in the ETS channel cache. The max_channels daemon option is consulted only by ssh_channel_sup:max_num_channels_not_exceeded/2, which counts supervisor children, so a channel that never gets a shell, exec, or subsystem handler is invisible to the limit and setting the option to a finite value does not mitigate the attack. RFC 4254 section 5.1 permits many session channels per connection, and each record costs only a few hundred bytes, so a single authenticated connection can accumulate channels until the node runs out of memory and the emulator terminates, affecting every application on it. No file contents, credentials, or write access are obtainable.\\n\\nThis issue affects OTP from OTP\\u00a018.1.2 before OTP\\u00a027.3.4.18, OTP\\u00a028.5.0.7, and OTP\\u00a029.1.1, corresponding to ssh from 4.1.1 before 5.2.11.13, 5.5.2.6, and 6.0.6. Whether OTP before OTP\\u00a018.1.2, corresponding to ssh before 4.1.1, is affected is unknown.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cp\u003eAllocation of Resources Without Limits or Throttling vulnerability in Erlang/OTP ssh allows an authenticated remote attacker to exhaust node memory by repeatedly opening session channels that are never assigned a handler.\u003c/p\u003e\\n\u003cp\u003eThe \u003ccode\u003e\\\"session\\\"\u003c/code\u003e clause of \u003ccode\u003essh_connection:handle_msg/4\u003c/code\u003e checks only \u003ccode\u003eminimal_remote_max_packet_size\u003c/code\u003e before calling \u003ccode\u003esetup_session/5\u003c/code\u003e, which unconditionally builds a \u003ccode\u003e#channel{}\u003c/code\u003e record and stores it in the ETS channel cache. The \u003ccode\u003emax_channels\u003c/code\u003e daemon option is consulted only by \u003ccode\u003essh_channel_sup:max_num_channels_not_exceeded/2\u003c/code\u003e, which counts supervisor children, so a channel that never gets a shell, exec, or subsystem handler is invisible to the limit and setting the option to a finite value does not mitigate the attack. RFC 4254 section 5.1 permits many session channels per connection, and each record costs only a few hundred bytes, so a single authenticated connection can accumulate channels until the node runs out of memory and the emulator terminates, affecting every application on it. No file contents, credentials, or write access are obtainable.\u003c/p\u003e\\n\u003cp\u003eThis issue affects OTP from OTP\u0026nbsp;18.1.2 before OTP\u0026nbsp;27.3.4.18, OTP\u0026nbsp;28.5.0.7, and OTP\u0026nbsp;29.1.1, corresponding to ssh from 4.1.1 before 5.2.11.13, 5.5.2.6, and 6.0.6. Whether OTP before OTP\u0026nbsp;18.1.2, corresponding to ssh before 4.1.1, is affected is unknown.\u003c/p\u003e\", \"base64\": false}, {\"type\": \"text/markdown\", \"value\": \"Allocation of Resources Without Limits or Throttling vulnerability in Erlang/OTP ssh allows an authenticated remote attacker to exhaust node memory by repeatedly opening session channels that are never assigned a handler.\\n\\nThe `\\\"session\\\"` clause of `ssh_connection:handle_msg/4` checks only `minimal_remote_max_packet_size` before calling `setup_session/5`, which unconditionally builds a `#channel{}` record and stores it in the ETS channel cache. The `max_channels` daemon option is consulted only by `ssh_channel_sup:max_num_channels_not_exceeded/2`, which counts supervisor children, so a channel that never gets a shell, exec, or subsystem handler is invisible to the limit and setting the option to a finite value does not mitigate the attack. RFC 4254 section 5.1 permits many session channels per connection, and each record costs only a few hundred bytes, so a single authenticated connection can accumulate channels until the node runs out of memory and the emulator terminates, affecting every application on it. No file contents, credentials, or write access are obtainable.\\n\\nThis issue affects OTP from OTP\\u00a018.1.2 before OTP\\u00a027.3.4.18, OTP\\u00a028.5.0.7, and OTP\\u00a029.1.1, corresponding to ssh from 4.1.1 before 5.2.11.13, 5.5.2.6, and 6.0.6. Whether OTP before OTP\\u00a018.1.2, corresponding to ssh before 4.1.1, is affected is unknown.\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-770\", \"description\": \"CWE-770 Allocation of Resources Without Limits or Throttling\"}]}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"27.3.4.18\"}, {\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"28.5.0.7\", \"versionStartIncluding\": \"28.0\"}, {\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"29.1.1\", \"versionStartIncluding\": \"29.0\"}], \"operator\": \"OR\"}], \"operator\": \"AND\"}], \"providerMetadata\": {\"orgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"shortName\": \"EEF\", \"dateUpdated\": \"2026-09-24T20:07:42.062Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2026-68956\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-09-24T20:07:42.062Z\", \"dateReserved\": \"2026-08-17T13:30:02.155Z\", \"assignerOrgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"datePublished\": \"2026-09-22T08:49:21.760Z\", \"assignerShortName\": \"EEF\"}",
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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