Answer in brief
CVE-2026-56855 records a High severity (CVSS 7.5) vulnerability in Prevent DoS on deadlocked established channel in golang.org/x/crypto/ssh. The current sources do not mark it as known exploited. The current feed maps golang.org/x/crypto/golang.org/x/crypto/ssh (generic), golang.org/x/crypto (go). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps golang.org/x/crypto/golang.org/x/crypto/ssh (generic), golang.org/x/crypto (go). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:a:golang:crypto:*:*:*:*:*:go:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| golang.org/x/crypto/golang.org/x/crypto/sshgeneric | >=0 <0.56.0 | 0.56.0 |
| golang.org/x/cryptogo | >=0 <0.56.0 | 0.56.0 |
Published upstream
Sep 2, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 24, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 2, 2026
Previously, after a channel has been established, a malicious peer could send crafted messages that would deadlock the entire connection. Now, we handle all RFC 4254 channel messages; global requests are handled explicitly. Then, treat all other messages as a protocol error and tear the connection down instead of buffering and blocking.
Quoted source text, attributed separately from HOL analysis.