russh: negotiating a MAC-requiring block cipher (CTR/CBC) with mac=none causes a slice-index-out-of-range panic (CVE-2026-102822) | HOL Guard CVE

Low · CVSS 3.7CVE-2026-102822

russh: negotiating a MAC-requiring block cipher (CTR/CBC) with mac=none causes a slice-index-out-of-range panic

Answer in brief

CVE-2026-102822 records a Low severity (CVSS 3.7) vulnerability in russh: negotiating a MAC-requiring block cipher (CTR/CBC) with mac=none causes a slice-index-out-of-range panic. The current sources do not mark it as known exploited. The current feed maps Eugeny/russh (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

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

Published Sep 29, 2026Updated Sep 29, 2026Source checked Sep 29, 2026First seen by HOL Sep 29, 2026Material review Sep 29, 2026

Upstream Advisory

Key facts

Risk: Low · CVSS 3.7
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 3.7. 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

The current feed maps Eugeny/russh (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Eugeny/russhgeneric	<0.63.1	0.63.1

Recommended response

Check inventory. Check lockfiles and deployed manifests for Eugeny/russh.
Review the reported fix. Update Eugeny/russh to 0.63.1 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 29, 2026

Sources and claim methodology

Upstream source description

Russh is a Rust SSH client and server library. Prior to 0.63.1, a connection configured to permit mac=none can negotiate it with a MAC-requiring CTR or CBC block cipher because the selection logic validates needs_mac() only when MAC selection fails. A remote peer can then send a packet with a decrypted length of zero, causing russh/src/cipher/mod.rs to shrink the previously read block before indexing buffer.buffer[16..], which panics and terminates the connection task. This issue is fixed in version 0.63.1.

Quoted source text, attributed separately from HOL analysis.