CVE-2026-44638 (GCVE-0-2026-44638)

Vulnerability from cvelistv5 – Published: 2026-05-14 19:59 – Updated: 2026-05-15 14:18
VLAI
Title
libsixel: NULL pointer dereference
Summary
libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, a wrong NULL check after an allocation call in sixel_decode_raw and sixel_decode causes a NULL pointer dereference whenever the allocation fails. The check tests the address of the output parameter (always non-NULL) instead of the value the malloc returned. On allocation failure, the function continues and writes through a NULL pointer, crashing the process. This is a denial of service against any caller of these public APIs that hits a low-memory condition. This vulnerability is fixed in 1.8.7-r2.
Severity
2.5 (Low)
CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L
SSVC
Exploitation: poc Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-15 14:17 UTC
CWE
  • CWE-476 - NULL Pointer Dereference
  • CWE-690 - Unchecked Return Value to NULL Pointer Dereference
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7637 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
saitoha libsixel Affected: >= 1.0.0, < 1.8.7-r2
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-44638",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-15T14:17:38.241135Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-15T14:18:03.581Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "libsixel",
          "vendor": "saitoha",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 1.0.0, \u003c 1.8.7-r2"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "libsixel is a SIXEL encoder/decoder implementation derived from kmiya\u0027s sixel. From  to 1.8.7-r1, a wrong NULL check after an allocation call in sixel_decode_raw and sixel_decode causes a NULL pointer dereference whenever the allocation fails. The check tests the address of the output parameter (always non-NULL) instead of the value the malloc returned. On allocation failure, the function continues and writes through a NULL pointer, crashing the process. This is a denial of service against any caller of these public APIs that hits a low-memory condition. This vulnerability is fixed in 1.8.7-r2."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "LOCAL",
            "availabilityImpact": "LOW",
            "baseScore": 2.5,
            "baseSeverity": "LOW",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-476",
              "description": "CWE-476: NULL Pointer Dereference",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-690",
              "description": "CWE-690: Unchecked Return Value to NULL Pointer Dereference",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-14T19:59:29.704Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w"
        }
      ],
      "source": {
        "advisory": "GHSA-wpx3-h5g8-qr3w",
        "discovery": "UNKNOWN"
      },
      "title": "libsixel: NULL pointer dereference"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-44638",
    "datePublished": "2026-05-14T19:59:29.704Z",
    "dateReserved": "2026-05-07T15:30:10.875Z",
    "dateUpdated": "2026-05-15T14:18:03.581Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-44638",
      "date": "2026-10-14",
      "epss": "0.00125",
      "percentile": "0.01975"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "product": "libsixel",
                "vendor": "saitoha",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003e= 1.0.0, \u003c 1.8.7-r2"
                  }
                ]
              }
            ],
            "source": "security-advisories@github.com"
          }
        ],
        "configurations": [
          {
            "nodes": [
              {
                "cpeMatch": [
                  {
                    "criteria": "cpe:2.3:a:saitoha:libsixel:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "07609BEC-B5AE-4004-8DF0-DCA17A16DF56",
                    "versionEndExcluding": "1.8.7-r2",
                    "versionStartIncluding": "1.0.0",
                    "vulnerable": true
                  }
                ],
                "negate": false,
                "operator": "OR"
              }
            ]
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "libsixel is a SIXEL encoder/decoder implementation derived from kmiya\u0027s sixel. From  to 1.8.7-r1, a wrong NULL check after an allocation call in sixel_decode_raw and sixel_decode causes a NULL pointer dereference whenever the allocation fails. The check tests the address of the output parameter (always non-NULL) instead of the value the malloc returned. On allocation failure, the function continues and writes through a NULL pointer, crashing the process. This is a denial of service against any caller of these public APIs that hits a low-memory condition. This vulnerability is fixed in 1.8.7-r2."
          }
        ],
        "id": "CVE-2026-44638",
        "lastModified": "2026-06-17T10:51:10.527",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "HIGH",
                "attackVector": "LOCAL",
                "availabilityImpact": "LOW",
                "baseScore": 2.5,
                "baseSeverity": "LOW",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "REQUIRED",
                "vectorString": "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L",
                "version": "3.1"
              },
              "exploitabilityScore": 1.0,
              "impactScore": 1.4,
              "source": "security-advisories@github.com",
              "type": "Secondary"
            },
            {
              "cvssData": {
                "attackComplexity": "HIGH",
                "attackVector": "LOCAL",
                "availabilityImpact": "LOW",
                "baseScore": 2.5,
                "baseSeverity": "LOW",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "REQUIRED",
                "vectorString": "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L",
                "version": "3.1"
              },
              "exploitabilityScore": 1.0,
              "impactScore": 1.4,
              "source": "nvd@nist.gov",
              "type": "Primary"
            }
          ],
          "ssvcV203": [
            {
              "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "ssvcData": {
                "id": "CVE-2026-44638",
                "options": [
                  {
                    "exploitation": "poc"
                  },
                  {
                    "automatable": "no"
                  },
                  {
                    "technicalImpact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-15T14:17:38.241135Z",
                "version": "2.0.3"
              }
            }
          ]
        },
        "published": "2026-05-14T20:17:08.983",
        "references": [
          {
            "source": "security-advisories@github.com",
            "tags": [
              "Exploit",
              "Vendor Advisory"
            ],
            "url": "https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w"
          },
          {
            "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
            "tags": [
              "Exploit",
              "Vendor Advisory"
            ],
            "url": "https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w"
          }
        ],
        "sourceIdentifier": "security-advisories@github.com",
        "vulnStatus": "Analyzed",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-476"
              },
              {
                "lang": "en",
                "value": "CWE-690"
              }
            ],
            "source": "security-advisories@github.com",
            "type": "Secondary"
          },
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-476"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "current_release_date": "2026-06-28T07:38:52+00:00",
      "cve": "CVE-2026-44638",
      "id": "CVE-2026-44638",
      "initial_release_date": "2026-05-14T19:59:29.704000+00:00",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "libsixel: libsixel: Denial of Service due to NULL pointer dereference during memory allocation",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44638.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2026-44638",
                    "options": [
                      {
                        "Exploitation": "poc"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-05-15T14:17:38.241135Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-05-15T14:17:56.807Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "references": [
              {
                "tags": [
                  "exploit"
                ],
                "url": "https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w"
              }
            ],
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "product": "libsixel",
              "vendor": "saitoha",
              "versions": [
                {
                  "status": "affected",
                  "version": "\u003e= 1.0.0, \u003c 1.8.7-r2"
                }
              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "libsixel is a SIXEL encoder/decoder implementation derived from kmiya\u0027s sixel. From  to 1.8.7-r1, a wrong NULL check after an allocation call in sixel_decode_raw and sixel_decode causes a NULL pointer dereference whenever the allocation fails. The check tests the address of the output parameter (always non-NULL) instead of the value the malloc returned. On allocation failure, the function continues and writes through a NULL pointer, crashing the process. This is a denial of service against any caller of these public APIs that hits a low-memory condition. This vulnerability is fixed in 1.8.7-r2."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "attackComplexity": "HIGH",
                "attackVector": "LOCAL",
                "availabilityImpact": "LOW",
                "baseScore": 2.5,
                "baseSeverity": "LOW",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "REQUIRED",
                "vectorString": "CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L",
                "version": "3.1"
              }
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-476",
                  "description": "CWE-476: NULL Pointer Dereference",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            },
            {
              "descriptions": [
                {
                  "cweId": "CWE-690",
                  "description": "CWE-690: Unchecked Return Value to NULL Pointer Dereference",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-05-14T19:59:29.704Z",
            "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
            "shortName": "GitHub_M"
          },
          "references": [
            {
              "name": "https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w",
              "tags": [
                "x_refsource_CONFIRM"
              ],
              "url": "https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w"
            }
          ],
          "source": {
            "advisory": "GHSA-wpx3-h5g8-qr3w",
            "discovery": "UNKNOWN"
          },
          "title": "libsixel: NULL pointer dereference"
        }
      },
      "cveMetadata": {
        "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "assignerShortName": "GitHub_M",
        "cveId": "CVE-2026-44638",
        "datePublished": "2026-05-14T19:59:29.704Z",
        "dateReserved": "2026-05-07T15:30:10.875Z",
        "dateUpdated": "2026-05-15T14:18:03.581Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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

JSON

Loading timeline…




    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.