KEVWire

Security intelligence, with context.

Response snapshot Oct 27, 2026, 05:48 UTC

Back to the wire
Permalink
VulnerabilityCVE-2026-112400

Pillow: GIF seek keeps rejected size after DecompressionBombError, allowing DoS

``` ============================================================================ GIF seek keeps rejected size after DecompressionBombError, allowing DoS Location: src/PIL/GifImagePlugin.py:293 in GifImageFile.

Published Updated

At a glance

Exploited
Not known
Severity
8.7 High (CVSS 4.0)
Chance of exploitation
0.5% 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-65qm-jvmh-6pqg (opens a new tab)

What happened

``` ============================================================================ GIF seek keeps rejected size after DecompressionBombError, allowing DoS Location: src/PIL/GifImagePlugin.py:293 in GifImageFile._seek() Commit: a707c6b21c313880d0771e54965d142dd42358b6 ============================================================================ ```

A GIF of about 60 bytes can make Pillow allocate gigabytes of memory. This affects applications that catch the "image too large" error raised while stepping to a later animation frame and then keep using the same image object. Pillow correctly refuses the oversized frame, but it stores the refused dimensions on the image object anyway, and later operations size their memory from them.

An attacker who can upload a GIF to such a service can exhaust its memory: the process either fails with an out-of-memory error after committing gigabytes, or is killed by the operating system. There is no memory corruption.

The bug is in `GifImageFile._seek()` (`src/PIL/GifImagePlugin.py:292-294`). When a frame's extent enlarges the image, the code assigns the new size to `self._size` and only then calls `Image._decompression_bomb_check()`. Nothing restores the old size when `DecompressionBombError` is raised, because `seek()` only rolls back on `EOFError`. After the caught error, `im.

Continue reading

size` reports the rejected size while the pixel buffer `im.im` is still the 1×1 first frame. Because the extent is a 16-bit offset plus a 16-bit size, that rejected size can be as large as 131070×131070.

In the attached reproducer, the rejected size is 40000×40000. A retried `seek(1)` followed by `load()` then reaches `load_prepare()`, which calls `Image.core.fill()` with that size to decode a single pixel. Peak memory rises from 17 MiB to 1700 MiB before a 3 GiB address-space cap stops the next allocation. `Image.new("RGB", im.size, ...)` and `rotate(..., expand=True)` also allocate from the stale size.

The default paths are unaffected: plain `Image.open()` plus `load()`, `ImageSequence.Iterator`, and `n_frames`/`is_animated`. The ordering was introduced in c9f1b35e9810 ("Added GIF decompression bomb check", 2022-06-30, first released in 9.2.0), the check added for CVE-2022-45198. The two dispose-extent checks later in the same function already validate before using the size, and the attached patch makes this check follow the same order.

## Details

`GifImageFile._seek()` lets a later frame enlarge the image, and performs the decompression-bomb check for the new size only *after* storing it on the object:

```python # src/PIL/GifImagePlugin.py:289-294 (GifImageFile._seek) x0, y0 = i16(s, 0), i16(s, 2) x1, y1 = x0 + i16(s, 4), y0 + i16(s, 6) if (x1 > self.size[0] or y1 > self.size[1]) and update_image: self._size = max(x1, self.size[0]), max(y1, self.size[1]) # state mutated Image._decompression_bomb_check(self._size) # ...then validated ```

`_decompression_bomb_check()` (`src/PIL/Image.py:3586`) raises `DecompressionBombError` for anything above `2 * MAX_IMAGE_PIXELS` (178 956 970 px by default), but by then `self._size` already holds the rejected value and nothing restores it: `seek()` (`GifImagePlugin.py:166-179`) only rolls back on `EOFError`, and `_seek(0)` only ever grows `_size`. The object that the application still holds therefore reports `im.

size == (40000, 40000)` while `im.im` is the 1×1 buffer of frame 0. Compare the two dispose-extent checks a few lines further down in the same function (`GifImagePlugin.py:383` and `:407`), which call `_decompression_bomb_check(dispose_size)` *before* the corresponding `Image.core.fill()`, and `TiffImagePlugin.load_prepare()` (`src/PIL/TiffImagePlugin.

py:1319-1321`), which checks `_tile_size` before allocating from it.

With this 60-byte GIF (hex)

``` 47494638396101000100800000000000ffffff GIF89a, 1x1 screen, 2-entry global palette 2c000000000100010000 02 024401 00 frame 0: 1x1 @ (0,0), LZW data 2c00000000409c409c00 frame 1 descriptor: 40000x40000 @ (0,0) 2c000000000100010000 02 024401 00 another 1x1 frame 3b trailer ```

`Image.open()` succeeds (`im.size == (1, 1)`), `im.seek(1)` raises `DecompressionBombError: Image size (1600000000 pixels) exceeds limit of 178956970 pixels`, and afterwards `im.size == (40000, 40000)`, `im.im.size == (1, 1)`, `im.tell() == 0`.

What happens next depends on what the application does with the object, but several ordinary operations take their dimensions from `im.size` rather than from the C buffer:

- Retrying `im.seek(1)`. The failed `_seek` left `self.__offset == 0` and the file pointer just past the 9-byte descriptor, so the retry parses whatever follows — in the file above, a valid 1×1 frame — and succeeds. `im.load()` then runs `GifImageFile.load_prepare()`: ```python # src/PIL/GifImagePlugin.py:452-456 elif self.mode in ("RGB", "RGBA"): self._prev_im = self.im if self._frame_palette: self.im = Image.core.

fill("P", self.size, self._frame_transparency or 0) ``` which allocates and `memset`s a 40000×40000 "P" image (1.6 GB) to decode a 1×1 tile into, and `load_end()` (`GifImagePlugin.py:485-491`) fills a second one and converts it to RGB (another 1.6 GB + 6.4 GB). - `im.rotate(angle, expand=True)` for a non-multiple-of-90 angle, or the common flatten-onto-background idiom `Image.new("RGB", im.

size, bg)`, allocate from `im.size` as well (measured on an object poisoned to 20000×20000: `rotate(45, expand=True)` completes and touches 776 MiB; `Image.new("RGB", im.size, "white")` touches 1.5 GiB). Operations that pass `im.size` as a box against the real buffer (`thumbnail`, `resize`, `save`) fail with `ValueError`/`SystemError` instead.

The extent fields are 16-bit offset plus 16-bit size, so the stored size can be pushed to 131070×131070 (17.2 Gpx; 17 GB for mode "P", 69 GB for "RGB"/"RGBA" storage), 96× the error threshold.

`n_frames` / `is_animated` are not affected: they call `_seek(frame, update_image=False)`, which skips the `_size` assignment (the file above reports `n_f

Affected package ranges reported by GitHub: Pillow: >= 9.2.0, < 13.0.0

Scores and how they were measured

CVSS base severity

8.7

Version 4.0As of

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/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

0.5%

Scored Percentile 43.4%

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-65qm-jvmh-6pqg (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-65qm-jvmh-6pqg, 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-65qm-jvmh-6pqg, 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-65qm-jvmh-6pqg, 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-65qm-jvmh-6pqg, 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-65qm-jvmh-6pqg, 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-65qm-jvmh-6pqg, 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-65qm-jvmh-6pqg, 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-65qm-jvmh-6pqg, 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-65qm-jvmh-6pqg, 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-65qm-jvmh-6pqg, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  12. Primary source

    NVD CVE-2026-112400 (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-2026-112400, 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: GIF seek keeps rejected size after DecompressionBombError, allowing DoS (CVE-2026-112400). https://kevwire.com/record/CVE-2026-112400

MLA

"Pillow: GIF seek keeps rejected size after DecompressionBombError, allowing DoS (CVE-2026-112400)." KEVWire, 20 Oct. 2026, kevwire.com/record/CVE-2026-112400.

Chicago

KEVWire. "Pillow: GIF seek keeps rejected size after DecompressionBombError, allowing DoS (CVE-2026-112400)." Last modified October 20, 2026. https://kevwire.com/record/CVE-2026-112400.

Evidence summary (plain text)

Pillow: GIF seek keeps rejected size after DecompressionBombError, allowing DoS (Oct 20, 2026).
```
============================================================================
GIF seek keeps rejected size after DecompressionBombError, allowing DoS
Location: src/PIL/GifImagePlugin.py:293 in GifImageFile._seek()
Commit: a707c6b21c313880d0771e54965d142dd42358b6
============================================================================
```

A GIF of about 60 bytes can make Pillow allocate gigabytes of memory. This affects applications that catch the "image too large" error raised while stepping to a later animation frame and then keep using the same image object. Pillow correctly refuses the oversized frame, but it stores the refused dimensions on the image object anyway, and later operations size their memory from them. An attacker who can upload a GIF to such a service can exhaust its memory: the process either fails with an out-of-memory error after committing gigabytes, or is killed by the operating system. There is no memory corruption.
CVSS 8.7 (version 4.0; evidence as of Oct 20, 2026; https://github.com/advisories/GHSA-65qm-jvmh-6pqg).
EPSS 0.5% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-112400&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-65qm-jvmh-6pqg: https://github.com/advisories/GHSA-65qm-jvmh-6pqg
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-2026-112400: https://nvd.nist.gov/vuln/detail/CVE-2026-112400
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-2026-112400&date=2026-10-26
Record ID: CVE-2026-112400.
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 27, 2026, 01:40 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.

Record JSON

Your account

Email alerts

Email alerts are not available yet. To follow your stack today, use its RSS feed, which honors your filters, or connect an AI agent through the API.

Suggest an improvement

Ideas, missing sources, corrections, and bugs are all welcome. No account needed. Suggestions are reviewed by a person before anything changes.

Record details

Record detail