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Response snapshot Oct 27, 2026, 00:37 UTC

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VulnerabilityCVE-2026-112404

Pillow: OOB read in TiffDecode.c tile and RGBA paths leaks heap memory into pixels

``` ============================================================================ OOB read in TiffDecode.c tile and RGBA paths leaks heap memory into pixels Location: src/libImaging/TiffDecode.

Published Updated

At a glance

Exploited
Not known
Severity
8.8 High (CVSS 4.0)
Chance of exploitation
0.4% in the next 30 days
Sources
2 independent sources

What to do

GitHub lists first patched versions: Pillow: 13.0.0. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-c6hw-5grf-ff96 (opens a new tab)

What happened

``` ============================================================================ OOB read in TiffDecode.c tile and RGBA paths leaks heap memory into pixels Location: src/libImaging/TiffDecode.c:483 in _decodeTile() Commit: a707c6b21c313880d0771e54965d142dd42358b6 ============================================================================ ```

Pillow reads past the end of a heap buffer when decoding certain malformed compressed TIFF files, and copies the bytes it reads into the pixels of the image it returns. An attacker who can get an application to open and load an image file, for example by uploading it to a service that returns thumbnails, previews or converted images, gets back fragments of that process's heap memory, including pointer values.

A slightly larger file instead crashes the process. No special settings are needed, and nothing is written out of bounds.

The bug is in `_decodeTile()` and `_decodeAsRGBA()` in `src/libImaging/TiffDecode.c`. Both size their decode buffer from libtiff's view of the pixel layout (`TIFFTileSize()`/`TIFFTileRowSize()`, or `img.width * 4`). They then unpack each row with the unpacker that `TiffImagePlugin.

Continue reading

_setup()` chose from Pillow's own parse of the directory, and neither checks that the unpacker's input row fits inside the row libtiff produced. `_decodeStrip()` has exactly this check, added for OSS-Fuzz `crash-0da0` in 8.2.0, but the tile and RGBA paths never got it.

The two parsers can be made to disagree with a duplicated `PhotometricInterpretation` or `BitsPerSample` tag, because libtiff keeps the first occurrence and Pillow keeps the last. Pillow then unpacks 4 to 8 bytes per pixel from rows that libtiff filled with 1 to 4 bytes, so the last rows of each tile are read from beyond the buffer.

The disclosed memory is a few tile rows past the buffer, and the attacker chooses the tile width. The amount does not grow with the number of tiles, because the buffer is reused for every tile.

The tile half was introduced in 1c295bf43 (first released in 8.2.0). The RGBA half was introduced in eb8c1206d, the CVE-2020-35654 fix (8.1.0).

The attached reproducer runs against an unmodified build. It writes three roughly 400-byte files that load without error, yet the last pixel rows of each change with glibc's malloc fill pattern and contain heap pointer bytes. A fourth file with a 65536x16 tile segfaults in `copy4` ← `_decodeTile` (`TiffDecode.c:483`) in most runs, depending on what is mapped after the buffer.

## Details

`_decodeTile()` and `_decodeAsRGBA()` in `src/libImaging/TiffDecode.c` size `state->buffer` from what libtiff says it will produce (`TIFFTileSize()`, resp. `img.width * 4`), but unpack each row with the shuffler that `TiffImagePlugin._setup()` selected from Pillow's *own* parse of the IFD.

Nothing in either function checks that the unpacker's input row (`width * state->bits / 8` bytes) fits inside the row libtiff wrote. `_decodeStrip()` has exactly that check; the other two do not.

Whenever the two IFD parsers disagree about the pixel layout — a tag with the wrong count or type that libtiff ignores but Pillow accepts, or a duplicated `PhotometricInterpretation`/`BitsPerSample`/`SamplesPerPixel` entry (libtiff keeps the first occurrence, `ImageFileDirectory_v2.load()` the last) — the unpacker reads past the end of the heap buffer and the bytes it reads become pixels of the returned image.

Any Pillow rawmode wider than libtiff's actual sample layout works (`RGBX`, `RGB;16N`, `RGBA;16N`, `I;32`, `F;32F`, …); `RGBA;16N` (64 bits/pixel) against 1-bit libtiff data is the largest ratio, where every row after the first of each tile is read almost entirely from beyond the buffer.

The ~400-byte TIFF `tile_count2.tif` generated by the reproducer — one 16x16 tile, `BitsPerSample 8`, `SamplesPerPixel 1`, `Compression 8` (Adobe Deflate), and `PhotometricInterpretation` written as a SHORT with **count 2** (`6, 6`) — is opened by `Image.open()` as mode `RGB` with libtiff rawmode `RGBX`, and `load()` succeeds on the stock build.

Rows 13–15 of the result contain bytes that lie 16, 32 and 48 bytes past the 256-byte tile buffer: decoding the same file twice under `MALLOC_PERTURB_=85` and `=170` yields identical rows 0–12 and different bytes in rows 13–15 (`aa` vs `55`, i.e. glibc's fill pattern). Under an ASan build of the extensions the same `load()` reports `heap-buffer-overflow READ of size 64` in `copy4` (`src/libImaging/Unpack.

c:1290`) called from `src/libImaging/TiffDecode.c:483`, against the 256-byte region allocated at `TiffDecode.c:448`. The same layout with a single 65536x16 tile (4.5 KB file) makes the stock build SIGSEGV in `copy4 ← _decodeTile` reading an unmapped address in most runs (whether it faults depends on what is mapped after the 1 MiB buffer; a wider tile makes it reliable).

### Why the two parsers disagree

libtiff 4.5 rejects a `PhotometricInterpretation` entry whose count is not 1 (`TIFFFetchNormalTag: Incorrect count for "PhotometricInterpretation"; tag ignored`), so for this file `TIFFGetField(tiff, TIFFTAG_PHOTOMETRIC, …)` returns 0 and libtiff treats the data as one 8-bit sample per pixel: `TIFFTileSize() = 256`, `TIFFTileRowSize() = 16`.

Pillow keeps the first value and carries on:

```python # src/PIL/TiffImagePlugin.py:762-770 (ImageFileDirectory_v2._setitem, reached from load()) try: (dest[tag],) = values except ValueError: # We've got a builtin tag with 1 expected entry warnings.warn(f"Metadata Warning, tag {tag} had too many entries: ...") dest[tag] = values[0] ```

so `_setup()` sees `photo == 6`. `OPEN_INFO[(II, 6, (1,), 1, (8,), ())]` is `("L", "L")`, and because the file is compressed the libtiff branch then overrides the rawmode:

```python # src/PIL/TiffImagePlugin.py:1578, 1600-1607 self.use_load_libtiff = READ_LIBTIFF or self._compression != "raw" … if photo == 6: self._mode = "RGB" if self._compression in "jpeg" and self._planar_configuration == 1: rawmode = "RGB" else: rawmode = "RGBX" ```

`

Affected package ranges reported by GitHub: Pillow: >= 8.1.0, < 13.0.0

Scores and how they were measured

CVSS base severity

8.8

Version 4.0As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.4%

Scored Percentile 32.4%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-c6hw-5grf-ff96 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c6hw-5grf-ff96, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c6hw-5grf-ff96, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  4. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c6hw-5grf-ff96, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  5. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c6hw-5grf-ff96, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  6. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c6hw-5grf-ff96, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  7. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c6hw-5grf-ff96, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  8. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c6hw-5grf-ff96, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  9. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c6hw-5grf-ff96, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  10. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c6hw-5grf-ff96, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  11. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c6hw-5grf-ff96, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  12. Primary source

    NVD CVE-2026-112404 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  13. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  14. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-112404, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 20). Pillow: OOB read in TiffDecode.c tile and RGBA paths leaks heap memory into pixels (CVE-2026-112404). https://kevwire.com/record/CVE-2026-112404

MLA

"Pillow: OOB read in TiffDecode.c tile and RGBA paths leaks heap memory into pixels (CVE-2026-112404)." KEVWire, 20 Oct. 2026, kevwire.com/record/CVE-2026-112404.

Chicago

KEVWire. "Pillow: OOB read in TiffDecode.c tile and RGBA paths leaks heap memory into pixels (CVE-2026-112404)." Last modified October 20, 2026. https://kevwire.com/record/CVE-2026-112404.

Evidence summary (plain text)

Pillow: OOB read in TiffDecode.c tile and RGBA paths leaks heap memory into pixels (Oct 20, 2026).
```
============================================================================
OOB read in TiffDecode.c tile and RGBA paths leaks heap memory into pixels
Location: src/libImaging/TiffDecode.c:483 in _decodeTile()
Commit: a707c6b21c313880d0771e54965d142dd42358b6
============================================================================
```

Pillow reads past the end of a heap buffer when decoding certain malformed compressed TIFF files, and copies the bytes it reads into the pixels of the image it returns. An attacker who can get an application to open and load an image file, for example by uploading it to a service that returns thumbnails, previews or converted images, gets back fragments of that process's heap memory, including pointer values. A slightly larger file instead crashes the process. No special settings are needed, and nothing is written out of bounds.
CVSS 8.8 (version 4.0; evidence as of Oct 20, 2026; https://github.com/advisories/GHSA-c6hw-5grf-ff96).
EPSS 0.4% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-112404&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-c6hw-5grf-ff96: https://github.com/advisories/GHSA-c6hw-5grf-ff96
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQxNTo1Mjo1NlrOAAfxiA%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQxNDowNjoxNFrOAAfxZw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQwODoyNzoyM1rOAAYp9A%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMTozNTo1OFrOAAfwCQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMTozMDoxM1rOAAfv2A%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMToyODowOVrOAAfv1g%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMToyNDoyMFrOAAfv1Q%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDo0NTowN1rOAAfvzQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDozMDoyNlrOAAfvxw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDowMzo1N1rOAAfvxQ%3D%3D
NVD CVE-2026-112404: https://nvd.nist.gov/vuln/detail/CVE-2026-112404
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?pubStartDate=2026-10-12T13:35:55.142Z&pubEndDate=2026-10-26T13:35:55.142Z&resultsPerPage=500&startIndex=5500
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-112404&date=2026-10-26
Record ID: CVE-2026-112404.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 19:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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