synced 9 MIN AGO
01 Record

CVE-2026-56866

HTTP/1 client connection desynchronization after CONNECT rejection in net/http

HighPUBLISHEDCNA: Go
CNA base score7.5 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
View raw JSON

02 Description

HTTP/1 client connection desynchronization after CONNECT rejection in net/http

03 Exploitation and scoring

Exploitation
Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.
SSVC decision
  • ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
  • AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
  • Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
0.47% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 40.6% of scored records. A rank, not a probability.
NVD base score
7.5 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD analysis status
Awaiting Analysis. NVD last modified this record on 2026-10-09.
Red Hat severity
Moderate. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2026-10-08 22:53Z20 DAYS AGO
Last updated
2026-10-09 15:54Z19 DAYS AGO
Reserved
2026-06-23
Assigning CNA
Go
Record state
PUBLISHED
Severity
High (CVSS 7.5)
CNA CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Weaknesses
  • CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')Base
Data version
5.2
Document digest
e3e4626a471ff24e9f80d8947cdfe39d010feaf2fba839784e40868059c2bb55

05 Affected products

VendorProductVersionsPlatforms
Go standard librarynet/http0 to < 1.26.9, 1.27.0-0 to < 1.27.2—
Go standard librarynet/http/httputil0 to < 1.26.9, 1.27.0-0 to < 1.27.2—

06 References

07 Fixed in

AlmaLinux 8

  • delve
    Fixed in 1.26.1-1.module_el8.10.0+4307+6e4cbc60
  • go-toolset
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang-bin
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang-docs
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang-misc
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang-race
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang-src
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang-tests
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60

Source: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.

AlmaLinux 9

  • go-toolset
    Fixed in 1.26.10-1.el9_8
  • golang
    Fixed in 1.26.10-1.el9_8
  • golang-bin
    Fixed in 1.26.10-1.el9_8
  • golang-docs
    Fixed in 1.26.10-1.el9_8
  • golang-misc
    Fixed in 1.26.10-1.el9_8
  • golang-race
    Fixed in 1.26.10-1.el9_8
  • golang-src
    Fixed in 1.26.10-1.el9_8
  • golang-tests
    Fixed in 1.26.10-1.el9_8

Source: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.

AlmaLinux 10

  • go-toolset
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang-bin
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang-docs
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang-misc
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang-race
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang-src
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang-tests
    Fixed in 1.26.10-1.el10_2.alma.1

Source: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.

CloudLinux 8

  • delve
    Fixed in 1.26.1-1.module_el8.10.0+4307+6e4cbc60
  • go-toolset
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang-bin
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang-docs
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang-misc
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang-race
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang-src
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60
  • golang-tests
    Fixed in 1.26.10-1.module_el8.10.0+4307+6e4cbc60

Derived from AlmaLinux 8. Partial coverage: only packages taken from AlmaLinux 8 are listed.

Source: CloudLinux errata, CloudLinux Inc. Derived from: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.

CloudLinux 9

  • go-toolset
    Fixed in 1.26.10-1.el9_8
  • golang
    Fixed in 1.26.10-1.el9_8
  • golang-bin
    Fixed in 1.26.10-1.el9_8
  • golang-docs
    Fixed in 1.26.10-1.el9_8
  • golang-misc
    Fixed in 1.26.10-1.el9_8
  • golang-race
    Fixed in 1.26.10-1.el9_8
  • golang-src
    Fixed in 1.26.10-1.el9_8
  • golang-tests
    Fixed in 1.26.10-1.el9_8

Derived from AlmaLinux 9. Partial coverage: only packages taken from AlmaLinux 9 are listed.

Source: CloudLinux errata, CloudLinux Inc. Derived from: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.

CloudLinux 10

  • go-toolset
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang-bin
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang-docs
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang-misc
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang-race
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang-src
    Fixed in 1.26.10-1.el10_2.alma.1
  • golang-tests
    Fixed in 1.26.10-1.el10_2.alma.1

Derived from AlmaLinux 10. Partial coverage: only packages taken from AlmaLinux 10 are listed.

Source: CloudLinux errata, CloudLinux Inc. Derived from: AlmaLinux, AlmaLinux OS. Copyright (c) 2023 AlmaLinux OS. Licensed under MIT License. Received through OSV.dev. Reformatted by exploit.cc.

Debian 12

  • golang-1.19
    No fix yet

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 13

  • golang-1.24
    No fix yet

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 14

  • golang-1.26
    Fixed in 1.26.9-1
  • golang-1.27
    Fixed in 1.27.2-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 14.04 LTS

  • golang-1.10
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 16.04 LTS

  • golang-1.10
    No fix yet
  • golang-1.6
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 18.04 LTS

  • golang-1.10
    No fix yet
  • golang-1.8
    No fix yet
  • golang-1.9
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 20.04 LTS

  • golang-1.13
    No fix yet
  • golang-1.14
    No fix yet
  • golang-1.18
    No fix yet
  • golang-1.20
    No fix yet
  • golang-1.21
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 22.04 LTS

  • golang-1.17
    No fix yet
  • golang-1.18
    No fix yet
  • golang-1.20
    No fix yet
  • golang-1.21
    No fix yet
  • golang-1.22
    Fixed in 1.22.2-2~22.04.4
  • golang-1.23
    No fix yet
  • golang-1.24
    No fix yet
  • golang-1.25
    No fix yet
  • golang-1.26
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 24.04 LTS

  • golang-1.21
    No fix yet
  • golang-1.22
    Fixed in 1.22.2-2ubuntu0.5
  • golang-1.23
    No fix yet
  • golang-1.24
    No fix yet
  • golang-1.25
    No fix yet
  • golang-1.26
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 26.04 LTS

  • golang-1.23
    No fix yet
  • golang-1.24
    No fix yet
  • golang-1.25
    No fix yet
  • golang-1.26
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 26.10

  • golang-1.26
    No fix yet
  • golang-1.27
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu Pro 16.04 LTS

  • golang-1.13
    No fix yet
  • golang-1.18
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu Pro 18.04 LTS

  • golang-1.13
    No fix yet
  • golang-1.16
    No fix yet
  • golang-1.18
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu Pro 20.04 LTS

  • golang-1.16
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu Pro 22.04 LTS

  • golang-1.13
    No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

A release or ecosystem missing from this list has no record here. It may be unaffected or not covered by the source. Source notices and licences.