vulnerability / NVI-00008935 / Revision 2
russh's SSH client is susceptible to unbounded allocations via EXT_INFO packets
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.
4.3 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
4.3 MEDIUM (3.1)
security-advisories@github.com severity; no combined Null risk score.
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
### 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.** Concretely, the evidence comes from executing the real russh v0.64.1 client packet parser (`Session::process_packet` handling `handle_ext_info`) in a live client session with attacker-supplied packet bodies in the pre-authentication state; the captured output below is from that real execution. russh's client stores every extension name it parses out of an `EXT_INFO` packet into a per-session vector and never clears, caps, or deduplicates it (`russh/src/client/encrypted.rs:433`, field declared at `russh/src/session.rs:60`). The packet is accepted without limit in the pre-authentication states, so a server - which is exactly the attacker position for a client library, and remains one even after the client has verified its host key - can send an unbounded sequence of these packets and grow the client's memory for as long as the session lives: 400 packets of about 26 KB each, carrying 3000 extension names apiece, retained 49.1 MiB (about 4.8 times the wire by
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. NIST National Vulnerability Database
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.
- NVD lastModified does not establish freshness of every associated CPE record.
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-4p9f-7p9m-5vfg ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2026-116773 ↗
NIST National Vulnerability Database · official catalog
Observed . This product uses data from the NVD API but is not endorsed or certified by the NVD.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 2 ·
Source facts changed; compare the preserved prior revision.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.