Critical
mbedtls — security advisory
An issue was discovered in Mbed TLS versions from 2.19.0 up to 3.6.5, Mbed TLS 4.0.0. Insufficient protection of serialized SSL context or session structures allows an attacker who can modify the serialized structures to induce memory corruption, leading to arbitrary code execution. This is caused by Incorrect Use of Privileged APIs.
- Products
- mbedtls
- Affected versions
- 2.1.2-1, 2.16.11-0.1ubuntu1, 2.16.11-0.3, 2.16.2-1, 2.16.3-1, 2.16.4-1ubuntu2, 2.16.4-1ubuntu2+esm1, 2.16.9-0.1ubuntu1, 2.2.0-1, 2.2.1-1, 2.2.1-2, 2.2.1-2ubuntu0.1, 2.2.1-2ubuntu0.2, 2.2.1-2ubuntu0.3, 2.28.0-1, 2.28.0-1build1, 2.28.0-1ubuntu0.1~esm1, 2.28.3-1, 2.28.6-1ubuntu1, 2.28.7-1.1ubuntu1, 2.28.7-1ubuntu1, 2.28.8-1, 2.28.8-1ubuntu0.1~esm1, 2.5.1-1ubuntu1, 2.6.0-1, 2.7.0-2, 2.8.0-1, 2.8.0-1ubuntu0.1~esm1, 3.6.2-3ubuntu1, 3.6.5-0.1ubuntu1, 3.6.5-0.1ubuntu2, 3.6.6-0.1ubuntu1, 3.6.7-3ubuntu1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-34877
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 02:08 UTC · Revision 1
Source evidence
An issue was discovered in Mbed TLS versions from 2.19.0 up to 3.6.5, Mbed TLS 4.0.0. Insufficient protection of serialized SSL context or session structures allows an attacker who can modify the serialized structures to induce memory corruption, leading to arbitrary code execution. This is caused by Incorrect Use of Privileged APIs.
osv:UBUNTU-CVE-2026-34877
mbedtls
Fixed versions: Not specified
mbedtls
Fixed versions: Not specified
mbedtls
Fixed versions: Not specified
mbedtls
Fixed versions: Not specified
mbedtls
Fixed versions: Not specified
mbedtls
Fixed versions: Not specified
mbedtls
Fixed versions: Not specified
mbedtls
Fixed versions: Not specified
Complete source record
{
"id": "f763f047d065805c667ee260eca77beca2b0f901082b970f10279102cfe08577",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-34877",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-34877",
"summary": "An issue was discovered in Mbed TLS versions from 2.19.0 up to 3.6.5, Mbed TLS 4.0.0. Insufficient protection of serialized SSL context or session structures allows an attacker who can modify the serialized structures to induce memory corruption, leading to arbitrary code execution. This is caused by Incorrect Use of Privileged APIs.",
"evidence": "osv:UBUNTU-CVE-2026-34877",
"products": [
{
"name": {
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"evidence": "/affected/0/package/name"
},
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{
"value": "2.1.2-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.2.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.2.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.2.1-2",
"evidence": "/affected/0/versions"
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{
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"evidence": "/affected/0/versions"
},
{
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{
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{
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{
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{
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{
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},
{
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}
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},
{
"name": {
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{
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{
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{
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{
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"affected_versions": [
{
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"evidence": "/affected/3/versions"
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{
"value": "2.16.11-0.1ubuntu1",
"evidence": "/affected/3/versions"
},
{
"value": "2.16.11-0.3",
"evidence": "/affected/3/versions"
},
{
"value": "2.28.0-1",
"evidence": "/affected/3/versions"
},
{
"value": "2.28.0-1build1",
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{
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{
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{
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"evidence": "/affected/4/versions"
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{
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"evidence": "/affected/4/versions"
},
{
"value": "2.28.7-1ubuntu1",
"evidence": "/affected/4/versions"
},
{
"value": "2.28.7-1.1ubuntu1",
"evidence": "/affected/4/versions"
},
{
"value": "2.28.8-1",
"evidence": "/affected/4/versions"
},
{
"value": "2.28.8-1ubuntu0.1~esm1",
"evidence": "/affected/4/versions"
}
]
},
{
"name": {
"value": "mbedtls",
"evidence": "/affected/5/package/name"
},
"prerequisites": [],
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"affected_versions": [
{
"value": "3.6.2-3ubuntu1",
"evidence": "/affected/5/versions"
}
]
},
{
"name": {
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"evidence": "/affected/6/package/name"
},
"prerequisites": [],
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"affected_versions": [
{
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"evidence": "/affected/6/versions"
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{
"value": "3.6.6-0.1ubuntu1",
"evidence": "/affected/6/versions"
},
{
"value": "3.6.7-3ubuntu1",
"evidence": "/affected/6/versions"
}
]
},
{
"name": {
"value": "mbedtls",
"evidence": "/affected/7/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.6.2-3ubuntu1",
"evidence": "/affected/7/versions"
},
{
"value": "3.6.5-0.1ubuntu1",
"evidence": "/affected/7/versions"
},
{
"value": "3.6.5-0.1ubuntu2",
"evidence": "/affected/7/versions"
}
]
}
],
"severity": "critical",
"structured": {
"id": "UBUNTU-CVE-2026-34877",
"aliases": [
"UBUNTU-CVE-2026-34877"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "mbedtls",
"purl": "pkg:deb/ubuntu/mbedtls?arch=source&distro=xenial",
"ecosystem": "Ubuntu:16.04:LTS"
},
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"2.2.0-1",
"2.2.1-1",
"2.2.1-2",
"2.2.1-2ubuntu0.1",
"2.2.1-2ubuntu0.2",
"2.2.1-2ubuntu0.3"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34877.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libmbedcrypto0",
"binary_version": "2.2.1-2ubuntu0.3"
},
{
"binary_name": "libmbedtls10",
"binary_version": "2.2.1-2ubuntu0.3"
},
{
"binary_name": "libmbedx509-0",
"binary_version": "2.2.1-2ubuntu0.3"
}
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}
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{
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"package": {
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"purl": "pkg:deb/ubuntu/mbedtls?arch=source&distro=esm-apps%2Fbionic",
"ecosystem": "Ubuntu:Pro:18.04:LTS"
},
"versions": [
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"2.7.0-2",
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"2.8.0-1ubuntu0.1~esm1"
],
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},
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{
"binary_name": "libmbedtls10",
"binary_version": "2.8.0-1ubuntu0.1~esm1"
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{
"binary_name": "libmbedx509-0",
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}
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{
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"package": {
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"ecosystem": "Ubuntu:Pro:20.04:LTS"
},
"versions": [
"2.16.2-1",
"2.16.3-1",
"2.16.4-1ubuntu2",
"2.16.4-1ubuntu2+esm1"
],
"database_specific": {
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},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libmbedcrypto3",
"binary_version": "2.16.4-1ubuntu2+esm1"
},
{
"binary_name": "libmbedtls12",
"binary_version": "2.16.4-1ubuntu2+esm1"
},
{
"binary_name": "libmbedx509-0",
"binary_version": "2.16.4-1ubuntu2+esm1"
}
]
}
},
{
"ranges": [
{
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}
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}
],
"package": {
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"ecosystem": "Ubuntu:Pro:22.04:LTS"
},
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"2.16.11-0.1ubuntu1",
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},
"ecosystem_specific": {
"binaries": [
{
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},
{
"binary_name": "libmbedtls14",
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},
{
"binary_name": "libmbedx509-1",
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{
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"ecosystem_specific": {
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{
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{
"binary_name": "libmbedtls14t64",
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{
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},
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],
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},
"ecosystem_specific": {
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{
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},
{
"binary_name": "libmbedtls21",
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},
{
"binary_name": "libmbedx509-7",
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]
}
},
{
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],
"package": {
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},
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},
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{
"binary_name": "libmbedcrypto16",
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},
{
"binary_name": "libmbedtls21",
"binary_version": "3.6.7-3ubuntu1"
},
{
"binary_name": "libmbedx509-7",
"binary_version": "3.6.7-3ubuntu1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
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{
"introduced": "0"
}
]
}
],
"package": {
"name": "mbedtls",
"purl": "pkg:deb/ubuntu/mbedtls?arch=source&distro=resolute",
"ecosystem": "Ubuntu:26.04:LTS"
},
"versions": [
"3.6.2-3ubuntu1",
"3.6.5-0.1ubuntu1",
"3.6.5-0.1ubuntu2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34877.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libmbedcrypto16",
"binary_version": "3.6.5-0.1ubuntu2"
},
{
"binary_name": "libmbedtls21",
"binary_version": "3.6.5-0.1ubuntu2"
},
{
"binary_name": "libmbedx509-7",
"binary_version": "3.6.5-0.1ubuntu2"
}
]
}
}
],
"modified": "2026-10-17T12:58:11.858180217Z",
"provider": "osv",
"upstream": [
"CVE-2026-34877"
],
"references": [
"https://ubuntu.com/security/CVE-2026-34877",
"https://www.cve.org/CVERecord?id=CVE-2026-34877",
"https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-serialized-data/"
]
},
"related_cves": [
{
"value": "CVE-2026-34877",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 358321,
"published_at": "2026-04-02T17:16:00+00:00"
}