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VulnerabilityPublished

CVE-2026-56853: Go standard library net/http · Unthrottled Resource Allocation

Affects Go standard library net/httpSource 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 net/http 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 net/http to 1.27.0-rc.3, 1.26.6 or 1.25.13.

Affected software

ProductAffectedFixed in
Go standard librarynet/httpAffected
  • >=1.27.0-0 <1.27.0-rc.3
Fixed in
  • 1.27.0-rc.3
Go standard librarynet/httpAffected
  • >=1.26.0-0 <1.26.6
Fixed in
  • 1.26.6
Go standard librarynet/httpAffected
  • <1.25.13
Fixed in
  • 1.25.13
Gonet/httppkg:golang/net/httpOther 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 disabling unencrypted HTTP/2 support or implementing external connection rate limiting to mitigate resource exhaustion risks.

Description

CVE-2026-56853 is a high-severity vulnerability in the Go standard library net/http package. It occurs when a server supports unencrypted HTTP/2 and reads initial bytes from new connections to detect the HTTP/2 client preface. During this process, the ReadHeaderTimeout setting is not applied as expected, leading to allocation of resources without proper limits or throttling. This can cause denial of service by exhausting server resources.

References

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