Vulnerability-Lookup

UBUNTU-CVE-2026-86805 (CVE-2026-86805)

Vulnerability from osv_ubuntu – Published: 2026-09-22 16:18 – Updated: 2026-09-22 16:18 – Source website

Details

A time-of-check to time-of-use (TOCTOU) race condition in the dynamic loader (ld.so) of the GNU C Library (glibc) versions 2.14 through 2.44 allows a local attacker to escalate privileges. When expanding $ORIGIN in DT_RPATH for setuid/setgid (AT_SECURE) programs, glibc validates the lexically normalized search path against the trusted directories but then opens the raw, un-normalized path. On systems where the Linux fs.protected_hardlinks sysctl is disabled, a local attacker who hard-links such a program into an attacker-controlled directory and wins a race to replace an intermediate path component with a symbolic link can direct the loader outside the trusted directory, causing it to load an attacker-controlled shared object and execute arbitrary code with the elevated privileges of the program. Exploitation requires an installed setuid or setgid binary whose DT_RPATH uses $ORIGIN followed by ".." traversal that normalizes into a trusted directory, and the ability to hard-link that binary and win the race by swapping a path component for a symbolic link. Major Linux-based OS distributions ship with fs.protected_hardlinks enabled by default and mitigate the vulnerability.

Severity

6.3 (Medium)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-86805	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-86805	REPORT
	https://sourceware.org/git/?p=glibc.git;a=blob;f=…	REPORT
	https://sourceware.org/bugzilla/show_bug.cgi?id=34360	REPORT
	https://sourceware.org/git/?p=glibc.git;a=blob_pl…	REPORT

JSON

To clipboard

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        "2.39-0ubuntu8.9"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "glibc-source",
            "binary_version": "2.43-2ubuntu2.4"
          },
          {
            "binary_name": "libc-bin",
            "binary_version": "2.43-2ubuntu2.4"
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            "binary_version": "2.43-2ubuntu2.4"
          },
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            "binary_name": "libc6-amd64",
            "binary_version": "2.43-2ubuntu2.4"
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            "binary_version": "2.43-2ubuntu2.4"
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            "binary_version": "2.43-2ubuntu2.4"
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            "binary_version": "2.43-2ubuntu2.4"
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            "binary_version": "2.43-2ubuntu2.4"
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            "binary_version": "2.43-2ubuntu2.4"
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        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "glibc",
        "purl": "pkg:deb/ubuntu/glibc@2.43-2ubuntu2.4?arch=source\u0026distro=resolute"
      },
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        {
          "events": [
            {
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            }
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          "type": "ECOSYSTEM"
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      ],
      "versions": [
        "2.42-0ubuntu3",
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        "2.42-2ubuntu2",
        "2.42-2ubuntu4",
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        "2.43-2ubuntu1",
        "2.43-2ubuntu2",
        "2.43-2ubuntu2.3",
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    }
  ],
  "aliases": [],
  "details": "A time-of-check to time-of-use (TOCTOU) race condition in the dynamic loader (ld.so) of the GNU C Library (glibc) versions 2.14 through 2.44 allows a local attacker to escalate privileges. When expanding $ORIGIN in DT_RPATH for setuid/setgid (AT_SECURE) programs, glibc validates the lexically normalized search path against the trusted directories but then opens the raw, un-normalized path. On systems where the Linux fs.protected_hardlinks sysctl is disabled, a local attacker who hard-links such a program into an attacker-controlled directory and wins a race to replace an intermediate path component with a symbolic link can direct the loader outside the trusted directory, causing it to load an attacker-controlled shared object and execute arbitrary code with the elevated privileges of the program. Exploitation requires an installed setuid or setgid binary whose DT_RPATH uses $ORIGIN followed by \"..\" traversal that normalizes into a trusted directory, and the ability to hard-link that binary and win the race by swapping a path component for a symbolic link. Major Linux-based OS distributions ship with fs.protected_hardlinks enabled by default and mitigate the vulnerability.",
  "id": "UBUNTU-CVE-2026-86805",
  "modified": "2026-09-22T16:18:00Z",
  "published": "2026-09-22T16:18:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-86805"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-86805"
    },
    {
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  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:L",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
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  ],
  "upstream": [
    "CVE-2026-86805"
  ]
}

CVE-2026-86805 (GCVE-0-2026-86805)

Vulnerability from cvelistv5 – Published: 2026-09-22 15:55 – Updated: 2026-09-23 03:55

Title

AT_SECURE programs may load attacker-controlled code via $ORIGIN

Summary

Severity

6.3 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-22 00:00 UTC

CWE

CWE-367 - Time-of-check time-of-use (TOCTOU) race condition

Assigner

glibc redhat root

References

2 references

URL	Tags
https://sourceware.org/bugzilla/show_bug.cgi?id=34360	issue-tracking
https://sourceware.org/git/?p=glibc.git;a=blob_pl…	vendor-advisory

Impacted products

1 product

Vendor	Product	Version
The GNU C Library	glibc	Affected: 2.14 , < 2.45 (custom)

Credits

Jann Horn

Show details on NVD website

JSON

To clipboard

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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.

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.

Action not permitted

UBUNTU-CVE-2026-86805 (CVE-2026-86805)

CVE-2026-86805 (GCVE-0-2026-86805)

Tags

Sightings

Nomenclature

Related by attack behaviour