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TI-2026-81531 Aliases CVE-2026-116696GHSA-9wfm-jcj8-jfv9

Unbounded memory growth in russh SSH agent server

Priority MEDIUM 49CWE-770Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · Low
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-770.

Summary

russh before 0.65.0, a Rust SSH client and server library, has an SSH agent server that appends every SSH_AGENT_CONSTRAIN_CONFIRM record sent while adding a key to a retained list without any count or memory limit (CWE-770). A process that can connect to the agent socket, including the remote side of a forwarded agent session, can repeat these records to cause memory growth that persists for the process lifetime, because keys without a lifetime constraint never expire.

Written with Claude Haiku 5.5 from the sources below · 2026-11-03

Description from the CNA

russh is a Rust SSH client and server library that includes an SSH agent protocol implementation. Prior to 0.65.0, russh::keys::agent::server::serve in russh/src/keys/agent/server.rs accepts repeated SSH_AGENT_CONSTRAIN_CONFIRM records while adding a key and appends every Constraint::Confirm record to the key's retained constraint vector without a count or memory limit. A process that can connect to the agent socket, including the remote side of a forwarded agent session, can repeatedly add constrained keys and cause renewable memory growth that persists for the process lifetime because keys without a lifetime constraint do not expire. This issue is fixed in version 0.65.0.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.0011 1st percentileScored 2026-11-07
Fix Fixed russh (Eugeny): 0.65.0russh (crates.io): 0.65.0Red Hat: 1 advisory

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
Eugenyrusshbefore 0.65.00.65.0Patch availableCNA
—russh (crates.io)before 0.65.00.65.0Patch availableGHSA-9wfm-jcj8-jfv9
  • russh VendorEugeny Affected before 0.65.0 Fixed in 0.65.0 Patch available CNA
  • russh (crates.io) Vendor— Affected before 0.65.0 Fixed in 0.65.0 Patch available GHSA-9wfm-jcj8-jfv9

Remediation

Upgrade russh to version 0.65.0, which fixes this for the Eugeny russh package and the crates.io russh package. Red Hat fixes Red Hat Hardened Images in RHSA-2026:93904, released 2026-11-02.

Written with Claude Haiku 5.5 from the sources below · 2026-11-03

  • Fix · CNA russh (Eugeny) Fixed in 0.65.0
  • Fix · GHSA-9wfm-jcj8-jfv9 russh (crates.io) Fixed in 0.65.0 Advisory →

Red Hat 1 advisory

  • RHSA-2026:93904 Released 2026-11-02 · Red Hat rating Moderate
    Red Hat Hardened Images RPMs Security Update
    • Red Hat Hardened Images openshell-0.1.6-0.1.hum1@aarch64, openshell-0.1.6-0.1.hum1@src, openshell-0.1.6-0.1.hum1@x86_64 +4

Vendor assessments

Red Hat

Red Hat rating: Low. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Hardened ImagesFixed RHSA-2026:93904

Timeline

  1. 2026-10-27 Threatist record created from CVE-2026-116696
  2. 2026-10-29 Affected versions changed · Red Hat
  3. 2026-10-29 CVSS score added · Red Hat
  4. 2026-10-30 Alias added: GHSA-9wfm-jcj8-jfv9
  5. 2026-10-30 Fix available: crates.io/[email protected] · GHSA-9wfm-jcj8-jfv9
  6. 2026-10-30 CVSS score added · GHSA-9wfm-jcj8-jfv9
  7. 2026-10-30 Weakness changed · GHSA-9wfm-jcj8-jfv9
  8. 2026-10-30 5 new references · GHSA-9wfm-jcj8-jfv9
  9. 2026-11-02 CISA SSVC decision points changed
  10. 2026-11-02 Priority changed: LOW → MEDIUM
  11. 2026-11-03 Fix available: RHSA-2026:93904 · Red Hat
  12. 2026-11-03 Fix available: Red Hat Hardened Images · Red Hat

References

Advisory 1

Other 4

  • TI-2026-65512 russh: Client-side channel-scoped Handler callbacks fire for channel IDs the client never opened CVSS 3.1HIGH 7.5
  • TI-2026-35550 Russh: SSH message fields were decoded through allocation-first parsers before field-specific bounds CVSS 3.1HIGH 7.5
  • TI-2026-34331 Russh: Post-decompression SSH packet size was not bounded, allowing remote oversized compressed packets CVSS 3.1HIGH 7.5
  • TI-2026-34308 Resource allocation without limits in Eugeny russh CVSS 3.1HIGH 7.5
  • TI-2025-16084 Tabby has a TCC Bypass via Misconfigured Node Fuses CVSS 4.0HIGH 8.6
  • TI-2024-36991 Tabby has a TCC Bypass via Unnecessary Permissive Entitlements in Tabby CVSS 4.0HIGH 8.6
See all 25 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences