Libssh: libssh: denial of service via zero advertised channel packet size (CVE-2026-59843) | HOL Guard CVE

Medium · CVSS 6.5CVE-2026-59843

Libssh: libssh: denial of service via zero advertised channel packet size

Answer in brief

CVE-2026-59843 records a Medium severity (CVSS 6.5) vulnerability in Libssh: libssh: denial of service via zero advertised channel packet size. The current sources do not mark it as known exploited. Affected software not mapped in the current feed; confirm the named product and version against your inventory.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jul 21, 2026Updated Sep 1, 2026Source checked Sep 27, 2026First seen by HOL Aug 12, 2026Material review Sep 1, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.5
Exploitation: Not marked as known exploited
Affected software: 5 mapped packages or products
Fix availability: Not reported

Why this deserves its current priority

CVSS is 6.5. 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.

Affected scope and exposure questions

Affected software not mapped in the current feed; confirm the named product and version against your inventory.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:a:libssh:libssh:-:::::::*	Not reported	Not reported
cpe:2.3:a:redhat:hardened_images:-:::::::*	Not reported	Not reported
cpe:2.3:o:redhat:enterprise_linux:10.0:::::::*	Not reported	Not reported
cpe:2.3:o:redhat:enterprise_linux:8.0:::::::*	Not reported	Not reported
cpe:2.3:o:redhat:enterprise_linux:9.0:::::::*	Not reported	Not reported

Recommended response

Confirm exposure. Identify whether the named product or interface exists in your inventory, then review the linked upstream references for affected versions and vendor guidance.

Evidence timeline and material changes

Published upstream
Jul 21, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 1, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 12, 2026

Sources and claim methodology

Upstream source description

A flaw was found in libssh. A remote authenticated peer can advertise a zero maximum packet size in SSH_MSG_CHANNEL_OPEN, causing later channel writes to loop indefinitely and consume CPU, leading to denial of service.

Quoted source text, attributed separately from HOL analysis.