UBUNTU-CVE-2026-55368

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Source
https://ubuntu.com/security/CVE-2026-55368
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55368.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-55368
Upstream
Published
2026-11-05T00:00:00Z
Modified
2026-11-06T01:01:07Z
Severity
  • 8.1 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 48b7ae12107fd2b118e4641da49599e9aac8edd8, H2O's access-log formatter could write past its log-line buffer when an affected custom access-log format was configured. The allocation errors affected %{error}x, %q when the query string was empty, and numeric elements whose temporary terminating NUL reached the end of the buffer. A matching request could crash the server, while the effect of the one-byte NUL overwrite beyond a crash was not established. This vulnerability is fixed with commit 48b7ae12107fd2b118e4641da49599e9aac8edd8.

References

Affected packages

Ubuntu:Pro:18.04:LTS / h2o

Package

Name
h2o
Purl
pkg:deb/ubuntu/h2o?arch=source&distro=esm-apps%2Fbionic

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

2.*
2.2.3+dfsg-2
2.2.4+dfsg-1
2.2.4+dfsg-1build1
2.2.4+dfsg-1ubuntu0.1~esm2

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "h2o",
            "binary_version": "2.2.4+dfsg-1ubuntu0.1~esm2"
        },
        {
            "binary_name": "libh2o-dev-common",
            "binary_version": "2.2.4+dfsg-1ubuntu0.1~esm2"
        },
        {
            "binary_name": "libh2o-evloop0.13",
            "binary_version": "2.2.4+dfsg-1ubuntu0.1~esm2"
        },
        {
            "binary_name": "libh2o0.13",
            "binary_version": "2.2.4+dfsg-1ubuntu0.1~esm2"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55368.json"

Ubuntu:Pro:20.04:LTS / h2o

Package

Name
h2o
Purl
pkg:deb/ubuntu/h2o?arch=source&distro=esm-apps%2Ffocal

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

2.*
2.2.5+dfsg2-3
2.2.5+dfsg2-3build1
2.2.5+dfsg2-3ubuntu0.1~esm1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "h2o",
            "binary_version": "2.2.5+dfsg2-3ubuntu0.1~esm1"
        },
        {
            "binary_name": "libh2o-dev-common",
            "binary_version": "2.2.5+dfsg2-3ubuntu0.1~esm1"
        },
        {
            "binary_name": "libh2o-evloop0.13",
            "binary_version": "2.2.5+dfsg2-3ubuntu0.1~esm1"
        },
        {
            "binary_name": "libh2o0.13",
            "binary_version": "2.2.5+dfsg2-3ubuntu0.1~esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55368.json"

Ubuntu:Pro:22.04:LTS / h2o

Package

Name
h2o
Purl
pkg:deb/ubuntu/h2o?arch=source&distro=esm-apps%2Fjammy

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

2.*
2.2.5+dfsg2-6
2.2.5+dfsg2-6.1
2.2.5+dfsg2-6.1ubuntu1
2.2.5+dfsg2-6.1ubuntu2
2.2.5+dfsg2-6.1ubuntu2+esm1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "h2o",
            "binary_version": "2.2.5+dfsg2-6.1ubuntu2+esm1"
        },
        {
            "binary_name": "libh2o-dev-common",
            "binary_version": "2.2.5+dfsg2-6.1ubuntu2+esm1"
        },
        {
            "binary_name": "libh2o-evloop0.13",
            "binary_version": "2.2.5+dfsg2-6.1ubuntu2+esm1"
        },
        {
            "binary_name": "libh2o0.13",
            "binary_version": "2.2.5+dfsg2-6.1ubuntu2+esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55368.json"

Ubuntu:24.04:LTS / h2o

Package

Name
h2o
Purl
pkg:deb/ubuntu/h2o?arch=source&distro=noble

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

2.*
2.2.5+dfsg2-7
2.2.5+dfsg2-8
2.2.5+dfsg2-8.1ubuntu1
2.2.5+dfsg2-8.1ubuntu2
2.2.5+dfsg2-8.1ubuntu3

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "h2o",
            "binary_version": "2.2.5+dfsg2-8.1ubuntu3"
        },
        {
            "binary_name": "libh2o-dev-common",
            "binary_version": "2.2.5+dfsg2-8.1ubuntu3"
        },
        {
            "binary_name": "libh2o-evloop0.13t64",
            "binary_version": "2.2.5+dfsg2-8.1ubuntu3"
        },
        {
            "binary_name": "libh2o0.13t64",
            "binary_version": "2.2.5+dfsg2-8.1ubuntu3"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55368.json"

Ubuntu:Pro:24.04:LTS / dnsdist

Package

Name
dnsdist
Purl
pkg:deb/ubuntu/dnsdist?arch=source&distro=esm-apps%2Fnoble

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.8.0-1
1.8.2-1
1.8.2-2
1.8.2-3
1.8.3-1
1.8.3-2
1.8.3-2build1
1.8.3-2build2
1.8.3-2ubuntu0.1~esm1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "dnsdist",
            "binary_version": "1.8.3-2ubuntu0.1~esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55368.json"