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CVE-2026-68956— SSH daemon allocates unbounded idle session channels, bypassing max_channels

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.

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

CVSS 7.1 · High EPSS 0.49% · P41

Affected Version Matrix 3

VendorProduct Version RangeStatus
Erlang OTP 18.1.2< * affected
4.1.1< * affected
84df3d4d0278e21a36a453bfee94799f0df67c2a< * affected
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I. Basic Information for CVE-2026-68956

Vulnerability Information

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Vulnerability Title
SSH daemon allocates unbounded idle session channels, bypassing max_channels
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
不加限制或调节的资源分配
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Erlang OTP 18.1.2 ~ * cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
Erlang OTP 4.1.1 ~ * cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
Erlang OTP 84df3d4d0278e21a36a453bfee94799f0df67c2a ~ * cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-68956

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III. Intelligence Information for CVE-2026-68956

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Patches & Fixes for CVE-2026-68956 (1)

Other References for CVE-2026-68956 (3)

Same Patch Batch · Erlang · 2026-09-22 · 3 CVEs total

CVE-2026-89422 9.3 CRITICAL TLS 1.3 client skips server authentication when ServerHello carries an unsolicited pre_sha
CVE-2026-65634 8.2 HIGH Superlinear CPU denial of service in Erlang/OTP ASN.1 OBJECT IDENTIFIER decoder

IV. Related Vulnerabilities

Same product: OTP
Same vendor: Erlang
Same weakness: CWE-770

V. Comments for CVE-2026-68956

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