Vulnerability-Lookup

CVE-2026-63383 (GCVE-0-2026-63383)

Vulnerability from cvelistv5 – Published: 2026-08-20 17:48 – Updated: 2026-08-20 18:41

Title

Libevent: decode_tag_internal() can lead to out-of-bounds read

Summary

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent can read beyond a contiguous evbuffer region in event_tagging.c when decode_tag_internal requests at most five bytes from evbuffer_pullup but iterates using the full logical buffer length. A fragmented evbuffer containing a six-byte malformed tag can therefore advance past the pullup window and trigger an out-of-bounds read, which can crash a process that decodes attacker-controlled tagged RPC data. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

Severity

8.7 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-20 18:37 UTC

CWE

CWE-125 - Out-of-bounds Read

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7760 records in the last 180 days details

References

5 references

URL	Tags
https://github.com/libevent/libevent/security/adv…	x_refsource_CONFIRM
https://github.com/libevent/libevent/commit/91ed8…	x_refsource_MISC
https://github.com/libevent/libevent/commit/e1f9e…	x_refsource_MISC
https://github.com/libevent/libevent/releases/tag…	x_refsource_MISC
https://github.com/libevent/libevent/releases/tag…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
libevent	libevent	Affected: >= 2.2.0-alpha, < 2.2.2-alpha Affected: < 2.1.13	guessed

Show details on NVD website

JSON

To clipboard

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}

RHSA-2026:72470

Vulnerability from csaf_redhat - Published: 2026-09-28 11:17 - Updated: 2026-10-17 14:34

Summary

Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.20.1

Severity

Important

Scope

59 vulnerabilities in this advisory, including CVE-2026-63383.

CVE-2026-63383

A flaw was found in Libevent, an event notification library. A remote attacker could exploit an out-of-bounds read vulnerability in the `decode_tag_internal()` function by sending specially crafted, attacker-controlled tagged RPC (Remote Procedure Call) data. This could lead to a denial of service, causing the process that decodes the data to crash.

7.5 (High)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Fixed: 8 products

https://access.redhat.com/errata/RHSA-2026:72470

Open the full advisory

RHSA-2026:72475

Vulnerability from csaf_redhat - Published: 2026-09-28 11:35 - Updated: 2026-10-17 14:34

Summary

Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.20.1

Severity

Important

Scope

63 vulnerabilities in this advisory, including CVE-2026-63383.

CVE-2026-63383

7.5 (High)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Fixed: 4 products

https://access.redhat.com/errata/RHSA-2026:72475

Open the full advisory

RHSA-2026:72476

Vulnerability from csaf_redhat - Published: 2026-09-28 11:36 - Updated: 2026-10-17 14:34

Summary

Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.20.1

Severity

Important

Scope

59 vulnerabilities in this advisory, including CVE-2026-63383.

CVE-2026-63383

7.5 (High)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Fixed: 4 products

https://access.redhat.com/errata/RHSA-2026:72476

Open the full advisory

UBUNTU-CVE-2026-63383 (CVE-2026-63383)

Vulnerability from osv_ubuntu – Published: 2026-08-21 00:00 – Updated: 2026-09-02 16:20 – Source website

Details

Severity

8.7 (High)


                    
                      CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-63383	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-63383	REPORT
	https://ubuntu.com/security/notices/USN-8710-1	ADVISORY

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "libevent-2.0-5",
            "binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm1"
          },
          {
            "binary_name": "libevent-core-2.0-5",
            "binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm1"
          },
          {
            "binary_name": "libevent-extra-2.0-5",
            "binary_version": "2.0.21-stable-1ubuntu1.14.04.2+esm1"
          },
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        ]
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        "ecosystem": "Ubuntu:Pro:14.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.0.21-stable-1ubuntu1.14.04.2+esm1?arch=source\u0026distro=esm-infra-legacy/trusty"
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        "2.0.21-stable-1",
        "2.0.21-stable-1ubuntu1",
        "2.0.21-stable-1ubuntu1.14.04.1",
        "2.0.21-stable-1ubuntu1.14.04.2"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro",
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            "binary_name": "libevent-2.0-5",
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        "2.0.21-stable-2",
        "2.0.21-stable-2ubuntu0.16.04.1"
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    },
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "libevent-2.1-6",
            "binary_version": "2.1.8-stable-4ubuntu0.1~esm1"
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            "binary_name": "libevent-core-2.1-6",
            "binary_version": "2.1.8-stable-4ubuntu0.1~esm1"
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            "binary_name": "libevent-extra-2.1-6",
            "binary_version": "2.1.8-stable-4ubuntu0.1~esm1"
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            "binary_name": "libevent-openssl-2.1-6",
            "binary_version": "2.1.8-stable-4ubuntu0.1~esm1"
          },
          {
            "binary_name": "libevent-pthreads-2.1-6",
            "binary_version": "2.1.8-stable-4ubuntu0.1~esm1"
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        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.1.8-stable-4ubuntu0.1~esm1?arch=source\u0026distro=esm-infra/bionic"
      },
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        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.1.8-stable-4ubuntu0.1~esm1"
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          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.1.8-stable-4",
        "2.1.8-stable-4build1"
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    },
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro",
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          {
            "binary_name": "libevent-2.1-7",
            "binary_version": "2.1.11-stable-1ubuntu0.1~esm1"
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            "binary_name": "libevent-core-2.1-7",
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            "binary_name": "libevent-extra-2.1-7",
            "binary_version": "2.1.11-stable-1ubuntu0.1~esm1"
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            "binary_version": "2.1.11-stable-1ubuntu0.1~esm1"
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            "binary_name": "libevent-pthreads-2.1-7",
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      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "libevent",
        "purl": "pkg:deb/ubuntu/libevent@2.1.11-stable-1ubuntu0.1~esm1?arch=source\u0026distro=esm-infra/focal"
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            {
              "fixed": "2.1.11-stable-1ubuntu0.1~esm1"
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          ],
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        }
      ],
      "versions": [
        "2.1.8-stable-4build1",
        "2.1.11-stable-1~exp0",
        "2.1.11-stable-1"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libevent-2.1-7",
            "binary_version": "2.1.12-stable-1ubuntu0.1"
          },
          {
            "binary_name": "libevent-core-2.1-7",
            "binary_version": "2.1.12-stable-1ubuntu0.1"
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        "availability": "No subscription required",
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        "name": "libevent",
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        "2.1.12-stable-10build1",
        "2.1.12-stable-10build2"
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    }
  ],
  "aliases": [],
  "details": "Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent can read beyond a contiguous evbuffer region in event_tagging.c when decode_tag_internal requests at most five bytes from evbuffer_pullup but iterates using the full logical buffer length. A fragmented evbuffer containing a six-byte malformed tag can therefore advance past the pullup window and trigger an out-of-bounds read, which can crash a process that decodes attacker-controlled tagged RPC data. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.",
  "id": "UBUNTU-CVE-2026-63383",
  "modified": "2026-09-02T16:20:06Z",
  "published": "2026-08-21T00:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-63383"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-63383"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-8710-1"
    }
  ],
  "related": [
    "USN-8710-1"
  ],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-63383"
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

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CVE-2026-63383 (GCVE-0-2026-63383)

RHSA-2026:72470

RHSA-2026:72475

RHSA-2026:72476

UBUNTU-CVE-2026-63383 (CVE-2026-63383)

Tags

Sightings

Nomenclature

Vulnerability timeline

Related by attack behaviour