Limit handshake messages we are willing to accept post-handshake in crypto/tls (CVE-2026-56862) | HOL Guard CVE

High · CVSS 7.5CVE-2026-56862

Limit handshake messages we are willing to accept post-handshake in crypto/tls

Answer in brief

CVE-2026-56862 records a High severity (CVSS 7.5) vulnerability in Limit handshake messages we are willing to accept post-handshake in crypto/tls. The current sources do not mark it as known exploited. The current feed maps Go standard library/crypto/tls (generic), stdlib (go). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

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

Published Aug 13, 2026Updated Sep 25, 2026Source checked Sep 28, 2026First seen by HOL Aug 13, 2026Material review Sep 25, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.5
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

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.

Affected scope and exposure questions

The current feed maps Go standard library/crypto/tls (generic), stdlib (go). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Go standard library/crypto/tlsgeneric	>=0 <1.25.13 \|\| >=1.26.0-0 <1.26.6 \|\| >=1.27.0-0 <1.27.0-rc.3	1.25.13, 1.26.6, 1.27.0-rc.3
stdlibgo	>=0 <1.25.13 >=1.26.0-0 <1.26.6 >=1.27.0-0 <1.27.0-rc.3	1.25.13, 1.26.6, 1.27.0-rc.3

Recommended response

Check inventory. Check lockfiles and deployed manifests for Go standard library/crypto/tls, stdlib.
Review the reported fix. Update Go standard library/crypto/tls to 1.25.13; stdlib to 1.25.13 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 13, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 13, 2026

Sources and claim methodology

Upstream source description

Handshake messages, such as KeyUpdate, are always considered as state-advancing, regardless of whether a handshake has been completed or not. As a result, a malicious client can keep sending KeyUpdate messages to force the server to keep performing key derivation operations indefinitely.

Quoted source text, attributed separately from HOL analysis.