Service interruption via unlimited post-handshake KeyUpdate processing
Published Aug 13, 2026 · Updated Aug 13, 2026
Resource exhaustion in Go standard library crypto/tls allows remote attackers to interrupt TLS 1.3 servers via repeated KeyUpdate messages. Conn.readRecordOrCCS counts each post-handshake KeyUpdate as state-advancing, so the non-advancing-record limit never stops repeated key derivation. An unauthenticated client must reach a TLS 1.3 server built with an affected Go release and can consume processing resources until the service becomes unavailable.
Summary
What happened
Resource exhaustion in Go standard library crypto/tls allows remote attackers to interrupt TLS 1.3 servers via repeated KeyUpdate messages. Conn.readRecordOrCCS counts each post-handshake KeyUpdate as state-advancing, so the non-advancing-record limit never stops repeated key derivation. An unauthenticated client must reach a TLS 1.3 server built with an affected Go release and can consume processing resources until the service becomes unavailable.
The record
- CVE
- CVE-2026-56862
- Published
- Aug 13, 2026
- Updated
- Aug 13, 2026
- Vendor
- Go standard library
- Product
- crypto/tls
- Classifications
- CWE-770, T1499.002
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 13, 2026CVE publishedPublication date reported by the CVE source.
- Aug 13, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <1.25.13
- Affected versionversion=1.26.0-0 <1.26.6
- Affected versionversion=1.27.0-0 <1.27.0-rc.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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