Vulnerability-Lookup

FKIE_CVE-2026-76844

Vulnerability from fkie_nvd - Published: 2026-08-24 14:17 - Updated: 2026-10-12 17:10

Severity

7.4 (High) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H

Summary

zlib 1.2.11 through 1.3.2 contains a heap buffer overflow: after an underlying write() fails, gz_write() returns without resetting strm.next_in, leaving it pointed at the caller's buffer. A later gz* write call then derives a position from the stale pointer and writes past a heap allocation; any write() failure reaches it, including EPIPE on a blocking descriptor, and in versions before 1.3.1.2 the failed write must be followed by a gzclearerr() call.

References

	URL	Tags
	disclosure@vulncheck.com	https://gist.github.com/thesmartshadow/e0b9481792afb7c31e86fee1ff084490
	disclosure@vulncheck.com	https://github.com/madler/zlib
	disclosure@vulncheck.com	https://github.com/madler/zlib/blob/v1.3.2/gzwrite.c#L393
	disclosure@vulncheck.com	https://github.com/madler/zlib/commit/df84af25dc1942490e1d1c899a07619152a46148
	disclosure@vulncheck.com	https://www.vulncheck.com/advisories/zlib-1.3.1.2-through-1.3.2-heap-buffer-overflow-via-gz-vacate

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:github/madler/zlib",
          "product": "zlib",
          "vendor": "zlib",
          "versions": [
            {
              "lessThanOrEqual": "1.3.2",
              "status": "affected",
              "version": "1.2.11",
              "versionType": "custom"
            }
          ]
        }
      ],
      "source": "disclosure@vulncheck.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "zlib 1.2.11 through 1.3.2 contains a heap buffer overflow: after an underlying write() fails, gz_write() returns without resetting strm.next_in, leaving it pointed at the caller\u0027s buffer. A later gz* write call then derives a position from the stale pointer and writes past a heap allocation; any write() failure reaches it, including EPIPE on a blocking descriptor, and in versions before 1.3.1.2 the failed write must be followed by a gzclearerr() call."
    },
    {
      "lang": "es",
      "value": "zlib 1.2.11 hasta 1.3.2 contiene un desbordamiento de b\u00fafer de mont\u00f3n: despu\u00e9s de que falle una llamada subyacente a write(), gz_write() retorna sin restablecer strm.next_in, dej\u00e1ndolo apuntando al b\u00fafer del llamador. Una llamada posterior de escritura gz entonces deriva una posici\u00f3n a partir del puntero obsoleto y escribe m\u00e1s all\u00e1 de una asignaci\u00f3n de mont\u00f3n; cualquier fallo de write() lo alcanza, incluyendo EPIPE en un descriptor de bloqueo, y en versiones anteriores a la 1.3.1.2 la escritura fallida debe ir seguida de una llamada a gzclearerr()."
    }
  ],
  "id": "CVE-2026-76844",
  "lastModified": "2026-10-12T17:10:00.163",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.4,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 5.2,
        "source": "disclosure@vulncheck.com",
        "type": "Primary"
      }
    ],
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "HIGH",
          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 8.3,
          "baseSeverity": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "HIGH",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-76844",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-26T18:22:33.313523Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-24T14:17:02.250",
  "references": [
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://gist.github.com/thesmartshadow/e0b9481792afb7c31e86fee1ff084490"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/madler/zlib"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/madler/zlib/blob/v1.3.2/gzwrite.c#L393"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/madler/zlib/commit/df84af25dc1942490e1d1c899a07619152a46148"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://www.vulncheck.com/advisories/zlib-1.3.1.2-through-1.3.2-heap-buffer-overflow-via-gz-vacate"
    }
  ],
  "sourceIdentifier": "disclosure@vulncheck.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-787"
        }
      ],
      "source": "disclosure@vulncheck.com",
      "type": "Primary"
    }
  ]
}

CVE-2026-76844 (GCVE-0-2026-76844)

Vulnerability from cvelistv5 – Published: 2026-08-24 13:12 – Updated: 2026-10-01 11:03

Title

zlib 1.2.11 through 1.3.2 Heap Buffer Overflow via Stale gzwrite Pointer After Failed Write

Summary

Severity

8.3 (High)


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

7.4 (High)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-26 18:22 UTC

CWE

CWE-787 - Out-of-bounds Write

Assigner

VulnCheck CNA under the mitre root

CNA scorecard B 84/100 over 5802 records in the last 180 days details

References

5 references

URL	Tags
https://gist.github.com/thesmartshadow/e0b9481792…	technical-descriptionexploit
https://github.com/madler/zlib/commit/df84af25dc1…	patch
https://github.com/madler/zlib/blob/v1.3.2/gzwrit…	technical-description
https://github.com/madler/zlib	product
https://www.vulncheck.com/advisories/zlib-1.3.1.2…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version
zlib	zlib	Affected: 1.2.11 , ≤ 1.3.2 (custom) cpe:2.3:a:zlib:zlib::::::::

Date Public

2026-09-02 00:00

Credits

Ali Firas (thesmartshadow) Michael Mullins

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-76844",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-26T18:22:33.313523Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-26T18:22:44.932Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:github/madler/zlib",
          "product": "zlib",
          "vendor": "zlib",
          "versions": [
            {
              "lessThanOrEqual": "1.3.2",
              "status": "affected",
              "version": "1.2.11",
              "versionType": "custom"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:zlib:zlib:*:*:*:*:*:*:*:*",
                  "versionEndIncluding": "1.3.2",
                  "versionStartIncluding": "1.2.11",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Ali Firas (thesmartshadow)"
        },
        {
          "lang": "en",
          "type": "finder",
          "value": "Michael Mullins"
        }
      ],
      "datePublic": "2026-09-02T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "zlib 1.2.11 through 1.3.2 contains a heap buffer overflow: after an underlying write() fails, gz_write() returns without resetting strm.next_in, leaving it pointed at the caller\u0027s buffer. A later gz* write call then derives a position from the stale pointer and writes past a heap allocation; any write() failure reaches it, including EPIPE on a blocking descriptor, and in versions before 1.3.1.2 the failed write must be followed by a gzclearerr() call."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "HIGH",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 8.3,
            "baseSeverity": "HIGH",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "HIGH"
          }
        },
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.4,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H",
            "version": "3.1"
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              "description": "Out-of-bounds Write",
              "lang": "en",
              "type": "CWE"
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      "references": [
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          "tags": [
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          "url": "https://gist.github.com/thesmartshadow/e0b9481792afb7c31e86fee1ff084490"
        },
        {
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        },
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          "tags": [
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    "assignerShortName": "VulnCheck",
    "cveId": "CVE-2026-76844",
    "datePublished": "2026-08-24T13:12:01.148Z",
    "dateReserved": "2026-08-19T20:34:19.724Z",
    "dateUpdated": "2026-10-01T11:03:59.221Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

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FKIE_CVE-2026-76844

CVE-2026-76844 (GCVE-0-2026-76844)

Tags

Sightings

Nomenclature

Related by attack behaviour