CVE-2026-102825 — Russh: Configured server auth-attempt cap is not enforced in the USERAUTH_REQUEST runtime path
Russh is a Rust SSH client and server library. Prior to 0.62.6, the USERAUTH_REQUEST path reached from server::run_stream in russh/src/server/encrypted.rs increments self.common.auth_attempts but never compares it with server::Config.max_auth_attempts. An unauthenticated remote client can continue submitting authentication requests on one connection beyond the configured cap, bypassing the deployment's attempt-limiting policy and increasing online guessing opportunity and backend authentication workload. This issue is fixed in version 0.62.6.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.3% (30-day exploitation probability)+3
- CISA SSVC: exploitation "poc"+5
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Eugeny Russh).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Search available logs for exploit probes matching the vulnerability class (authentication), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 3.7 | CVSS 3.1 | Low | 2.2 | 1.4 | security-advisories@github.com via NIST National Vulnerability Database |
| 3.7 | CVSS 3.1 | Low | — | — | GitHub_M via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N (score shown at the top: security-advisories@github.com) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
CWE-307 · Improper Restriction of Excessive Authentication Attempts
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Review authentication logs: logins without MFA, anomalous sessions and recently created accounts.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · eugeny/russh
- SSVC assessment updated
- Record published
- CVSS changed · 3.7
- Source status changed · → Deferred
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 15, 2026 – Oct 15, 2026
References
3 on the record
Elsewhere on this site
Related CVEs (same products)
- Medium CVE-2026-102824 Russh: Missing X25519 zero-point validation in hybrid ML-KEM key exchange 17d
- High CVE-2026-102823 russh: Client-side channel-scoped Handler callbacks fire for channel IDs the client never opened 17d
- Low CVE-2026-102822 russh: negotiating a MAC-requiring block cipher (CTR/CBC) with mac=none causes a slice-index-out-of-range panic 17d
- Medium CVE-2026-102821 Russh: Unbounded memory exhaustion via CHANNEL_OPEN flood during a client-stalled rekey 17d
- Medium CVE-2026-102820 pageant: Out-of-bounds read / oversized allocation in `pageant` MemoryMap::read via a malicious Pageant agent (Windows) 17d
- Medium CVE-2026-73489 Russh: Post-auth remote panic via pty-req with more than 130 terminal-mode records Aug 13, 2026
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No fixed version, patch or mitigation documented.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-102825 is "Russh: Configured server auth-attempt cap is not enforced in the USERAUTH_REQUEST runtime path", rated Low. It affects Russh (Eugeny); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 3.7 describes technical severity. EPSS 0.28% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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