vulnerability / NVI-00009158 / Revision 2
russh's SSH agent server is susceptible to unbound allocations via repeated SSH_AGENT_CONSTRAIN_CONFIRM messages
GitHub lists this reviewed advisory for russh. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
3.3 low
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
0.110%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.01255. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
russh
source listed< 0.65.0
### Summary **All evidence, reproduction steps, and scripts in the report were verified against a real running instance. Nothing is fabricated or synthetic; every verdict is backed by captured output from an actual deployment.** The SSH agent server that ships with russh (`russh::keys::agent::server::serve`) parses client key-addition requests and, for each `SSH_AGENT_CONSTRAIN_CONFIRM` (0x02) record it finds, pushes one `Constraint::Confirm` value into a per-key vector inside an unbounded loop, then stores the resulting pair permanently in its keystore (`russh/src/keys/agent/server.rs:296-303`). Neither the constraint vector nor the keystore has a size or count limit: the only boundary is the 256 KiB agent frame cap, and every 1-byte record a client sends becomes a 56-byte enum retained for the life of the process. Any process that can connect to the agent socket - the same trust model the project itself established when fixing a prior advisory about this same request handler - can therefore grow the agent's memory without bound and renew the growth at will: six 256 KiB requests retained 72.4 MiB (about 12.1 MiB per request, a roughly 48-fold amplification) while an equal number
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-9wfm-jcj8-jfv9 ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2026-116696 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 2 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.