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VulnerabilityPublished

CVE-2026-56862: Go standard library crypto/tls · Unthrottled Resource Allocation

Affects Go standard library crypto/tlsSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High · fixed in 1.27.0-rc.3 : patch Go standard library crypto/tls soon.

Data as of 12 Nov 2026, 23:24 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.5% chance of exploitation in 30 days – higher than 47% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 1.27.0-rc.3, 1.26.6, 1.25.13
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 13 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

What to do

Upgrade Go standard library crypto/tls to 1.27.0-rc.3, 1.26.6 or 1.25.13.

Affected software

ProductAffectedFixed in
Go standard librarycrypto/tlsAffected
  • >=1.27.0-0 <1.27.0-rc.3
Fixed in
  • 1.27.0-rc.3
Go standard librarycrypto/tlsAffected
  • >=1.26.0-0 <1.26.6
Fixed in
  • 1.26.6
Go standard librarycrypto/tlsAffected
  • <1.25.13
Fixed in
  • 1.25.13
Gocrypto/tlspkg:golang/crypto/tlsOther threatsAffected
  • <1.25.13
  • >=1.26.0-0 <1.26.6
  • >=1.27.0-0 <1.27.0-rc.3
Fixed in
  • 1.25.13
  • 1.26.6
  • 1.27.0-rc.3

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, consider implementing rate limiting or other controls at the application or network level to mitigate potential resource exhaustion from repeated KeyUpdate messages.

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.

References

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