EUVD-2026-36131
GHSA-4r3c-5hpg-58qr
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
-
AccessIdentify russh-backed SSH endpoint
-
DeliveryOpen TCP connection to SSH port
-
ExploitSend malformed length-prefixed name-list/string
-
ExecutionDecoder over-allocates before bounds check
-
PersistProcess OOM or panic
-
ImpactService unavailable to legitimate users
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V2 - Validation and Business Logic Input validation, allowlisting
|
| Exploitation Conditions | Exploitation requires only the ability to send SSH protocol messages to a russh-based endpoint - either a russh server reachable on its listening port (no authentication required, as the malformed fields are parsed during pre-auth message handling), or a russh client that connects out to an attacker-controlled SSH server. The target must run russh 0.34.0 through 0.60.x; russh users on <0.34.0 or >=0.61.0 are not affected. Limiting factors: the impact is denial of service only (no code execution, no data disclosure per CVSS C:N/I:N), the target must actually be built on russh rather than OpenSSH or another SSH stack, and exposure narrows substantially if the SSH listener is firewalled to trusted source networks. |
| Impact | The CVSS vector AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H is internally consistent: SSH is network-reachable, the malformed packets can be sent at the transport/auth layer (no credentials needed against a server build, and a malicious server can attack a client during banner/key-exchange), and only availability is impacted. EPSS and CISA KEV data were not provided, and no public PoC reference appears in the input, so real-world exploitation pressure is currently unknown - treat as no public exploit identified at time of analysis. Practical priority depends on exposure: Russh-based servers reachable from untrusted networks should patch promptly because the attack is pre-authentication; embedded client use against trusted endpoints is lower urgency. The advisory tag 'Information Disclosure' in the input conflicts with the CVSS C:N rating and the description (which describes allocation/DoS behavior, not disclosure) - defenders should rely on the CVSS impact metrics and the GHSA text rather than the tag. |
| Exploit ScenarioDerived | An attacker scans the internet for SSH services backed by russh and opens a TCP connection to the SSH port; before completing authentication, they send a crafted SSH packet whose length-prefixed name-list or byte string declares an enormous or high-fanout size. The russh decoder attempts to allocate or split the buffer before bounds-checking, causing the process to OOM or panic and terminating service for legitimate users; repeating the connection cheaply sustains the outage. |
Get an e-mail when this CVE is exploited, patched or re-scored. Free account.
Alert meAnalysisAIv1 – Jun 10, 2026
Denial of service in Russh (Rust SSH client/server library) versions 0.34.0 through 0.60.x allows remote SSH peers to trigger excessive memory allocation by sending oversized, high-fanout, or malformed length-prefixed SSH strings, name-lists, and byte fields before field-specific bounds checks are applied. The flaw affects both client and server message handlers and impacts availability only (CVSS 7.5, C:N/I:N/A:H). No public exploit identified at time of analysis.
RemediationAI
Vendor-released patch: russh 0.61.0 - upgrade the russh dependency in Cargo.toml to >=0.61.0 and rebuild/redeploy all consuming binaries (cargo update -p russh), then verify the lockfile no longer references a 0.34.0-0.60.x release. Consult the GHSA at https://github.com/Eugeny/russh/security/advisories/GHSA-4r3c-5hpg-58qr for the exact patched commits. If immediate upgrade is not possible, compensating controls include restricting inbound SSH to known source IPs at the firewall (reduces but does not eliminate exposure if any allowed peer is malicious), placing the russh-based server behind a hardened SSH bastion or proxy that terminates and re-frames SSH (adds latency and operational complexity), and applying per-process memory cgroup/ulimit caps so an over-allocation crashes only the worker rather than the host (causes legitimate sessions to fail under load). For russh used as a client, avoid connecting to untrusted SSH servers until patched.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in cargo
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
Russh is a pure-Rust implementation of the SSH2 protocol used as both a client and server library, typically embedded in applications that need programmatic SSH (e.g., bastions, automation, custom servers). The root cause is CWE-20 (Improper Input Validation): the SSH wire format uses length-prefixed strings, name-lists, and byte arrays (RFC 4251 §5), and Russh's decoders allocated owned buffers sized from those attacker-controlled length fields - or eagerly split/iterated over high-fanout name-lists - before enforcing the per-field maximums that the protocol logic later expected. This lets a peer drive the process toward over-allocation during the early decode stage rather than being rejected at the framing layer.
Know when Russh gets its next vulnerability
- Watch products and get an email when something new is published
- Check this CVE against your own stack and servers
- Exploit and PoC references, threat intelligence from 22 sources
No credit card · 7-day full trial
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Pre-auth SSH decode flaw reachable over the network with no user interaction; impact is availability-only via over-allocation, with no confidentiality or integrity effect.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
Lifecycle Timeline
1DescriptionCVE.org
Russh is a Rust SSH client & server library. From version 0.34.0 to before version 0.61.0, several russh client and server message handlers decoded attacker-controlled SSH strings, name-lists, and byte fields into owned allocations before applying field-specific bounds. A remote SSH peer could send oversized, high-fanout, or malformed length-prefixed fields and make the library allocate, attempt to allocate, or split data before rejecting input that should have been rejected earlier. This issue has been patched in version 0.61.0.
Executive ViewAI
Russh SSH library versions 0.34.0 through 0.60.x contain a denial-of-service vulnerability enabling remote attackers to exhaust memory on both client and server implementations via malformed SSH protocol messages, directly threatening network availability and continuity of SSH-dependent services. No public exploit has been identified at time of analysis, but organizations deploying affected versions face potential service disruption as no vendor patch is currently available.
Implement network-level access controls restricting SSH connectivity to trusted peers; deploy SSH connection rate limiting and per-peer resource quotas to mitigate memory exhaustion; establish monitoring and alerting for memory and CPU anomalies on SSH services; consider temporary migration to alternative SSH server implementations for critical systems pending patch availability.
Threat Intelligence Overview
NVD
CVE.org
EPSS
Vulnrichment
VulDB
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.
The SSH transport protocol with certain OpenSSH extensions, found in OpenSSH before 9.6 and other products, allows remot
Russh is a Rust SSH client & server library. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable,
russh is a Rust SSH client and server library. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploita
Unauthenticated remote denial of service in the Russh SSH library (versions ≤ 0.62.3) allows any network attacker to cra
Denial-of-service in russh's Curve25519 key exchange client path allows any malicious SSH server to crash a connecting r
russh's SSH agent server signs with keys loaded under the confirm constraint without ever invoking the application's app
Improper validation in the Russh Rust SSH library (versions prior to 0.63.1) lets a malicious or compromised SSH server
Pre-authentication denial-of-service in russh SSH server library allows remote attackers to crash servers implementing k
Denial of service in Russh (versions 0.37.0-0.60.x), a Rust SSH client and server library, allows a malicious SSH server
Memory exhaustion in the Russh Rust SSH client/server library prior to 0.63.2 allows an authenticated remote peer to sta
The Windows Pageant client inside the pageant Rust crate (pageant/src/wmmessage.rs) trusts a peer-controlled u32 respons
Resource exhaustion in Russh's SSH server identification-string reader allows unauthenticated remote attackers to hold c
Exploit-DB