CVE-2026-33123

pypdf has inefficient decoding of array-based streams

pypdf is a free and open-source pure-python PDF library. Versions prior to 6.9.1 allow an attacker to craft a malicious PDF which leads to long runtimes and/or large memory usage. Exploitation requires accessing an array-based stream with many entries. This issue has been fixed in version 6.9.1.

CVSS 4.0 · 5.1 Medium EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2026-31826

pypdf: manipulated stream length values can exhaust RAM

pypdf is a free and open-source pure-python PDF library. Prior to 6.8.0, an attacker who uses this vulnerability can craft a PDF which leads to large memory usage. This requires parsing a content stream with a rather large /Length value, regardless of the actual data length inside the stream. This vulnerability is fixed in 6.8.0.

CVSS 4.0 · 6.8 Medium EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2026-28804

pypdf: Inefficient decoding of ASCIIHexDecode streams

pypdf is a free and open-source pure-python PDF library. Prior to version 6.7.5, an attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires accessing a stream which uses the /ASCIIHexDecode filter. This issue has been patched in version 6.7.5.

CVSS 4.0 · 6.9 Medium EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2026-28351

Manipulated RunLengthDecode streams can exhaust RAM

pypdf is a free and open-source pure-python PDF library. Prior to version 6.7.4, an attacker who uses this vulnerability can craft a PDF which leads to large memory usage. This requires parsing the content stream using the RunLengthDecode filter. This has been fixed in pypdf 6.7.4. As a workaround, consider applying the changes from PR #3664.

CVSS 4.0 · 6.9 Medium EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2026-27888

pypdf: Manipulated FlateDecode XFA streams can exhaust RAM

pypdf is a free and open-source pure-python PDF library. Prior to 6.7.3, an attacker who uses this vulnerability can craft a PDF which leads to the RAM being exhausted. This requires accessing the `xfa` property of a reader or writer and the corresponding stream being compressed using `/FlateDecode`. This has been fixed in pypdf 6.7.3. As a workaround, apply the patch manually.

CVSS 4.0 · 6.6 Medium EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2026-27628

pypdf has a possible infinite loop when loading circular /Prev entries in cross-reference streams

pypdf is a free and open-source pure-python PDF library. Prior to 6.7.2, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires reading the file. This has been fixed in pypdf 6.7.2. As a workaround, one may apply the patch manually.

CVSS 4.0 · 1.2 Low EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2026-27026

pypdf possibly has long runtimes for malformed FlateDecode streams

pypdf is a free and open-source pure-python PDF library. Prior to 6.7.1, an attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a malformed /FlateDecode stream, where the byte-by-byte decompression is used. This vulnerability is fixed in 6.7.1.

CVSS 4.0 · 6.9 Medium EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2026-27025

pypdf has possible long runtimes/large memory usage for large /ToUnicode streams

pypdf is a free and open-source pure-python PDF library. Prior to 6.7.1, an attacker who uses this vulnerability can craft a PDF which leads to long runtimes and large memory consumption. This requires parsing the /ToUnicode entry of a font with unusually large values, for example during text extraction. This vulnerability is fixed in 6.7.1.

CVSS 4.0 · 6.9 Medium EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2026-27024

pypdf has a possible infinite loop when processing TreeObject

pypdf is a free and open-source pure-python PDF library. Prior to 6.7.1, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires accessing the children of a TreeObject, for example as part of outlines. This vulnerability is fixed in 6.7.1.

CVSS 4.0 · 6.9 Medium EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2026-24688

pypdf has possible Infinite Loop when processing outlines/bookmarks

pypdf is a free and open-source pure-python PDF library. An attacker who uses an infinite loop vulnerability that is present in versions prior to 6.6.2 can craft a PDF which leads to an infinite loop. This requires accessing the outlines/bookmarks. This has been fixed in pypdf 6.6.2. If projects cannot upgrade yet, consider applying the changes from PR #3610 manually.

CVSS 4.0 · 5.1 Medium EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2026-22691

pypdf has possible long runtimes for malformed startxref

pypdf is a free and open-source pure-python PDF library. Prior to version 6.6.0, pypdf has possible long runtimes for malformed startxref. An attacker who uses this vulnerability can craft a PDF which leads to possibly long runtimes for invalid startxref entries. When rebuilding the cross-reference table, PDF files with lots of whitespace characters become problematic. Only the non-strict reading mode is affected. Only the non-strict reading mode is affected. This issue has been patched in version 6.6.0.

CVSS 4.0 · 2.7 Low EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2026-22690

pypdf has possible long runtimes for missing /Root object with large /Size values

pypdf is a free and open-source pure-python PDF library. Prior to version 6.6.0, pypdf has possible long runtimes for missing /Root object with large /Size values. An attacker who uses this vulnerability can craft a PDF which leads to possibly long runtimes for actually invalid files. This can be achieved by omitting the /Root entry in the trailer, while using a rather large /Size value. Only the non-strict reading mode is affected. This issue has been patched in version 6.6.0.

CVSS 4.0 · 2.7 Low EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2023-36464

Infinite Loop when a comment isn't followed by a character in pypdf

pypdf is an open source, pure-python PDF library. In affected versions an attacker may craft a PDF which leads to an infinite loop if `__parse_content_stream` is executed. That is, for example, the case if the user extracted text from such a PDF. This issue was introduced in pull request #969 and resolved in pull request #1828. Users are advised to upgrade. Users unable to upgrade may modify the line `while peek not in (b"\r", b"\n")` in `pypdf/generic/_data_structures.py` to `while peek not in (b"\r", b"\n", b"")`.

CVSS 3.1 · 6.2 Medium EPSS < 1% KEV · Not listed

Vendors

Py-pdf Pypdf2 Project

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Pypdf Pypdf2

CVE-2023-36807

Infinite Loop when reading malformed objects in pypdf

pypdf is a pure-python PDF library capable of splitting, merging, cropping, and transforming the pages of PDF files. In version 2.10.5 an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This infinite loop blocks the current process and can utilize a single core of the CPU by 100%. It does not affect memory usage. That is, for example, the case if the user extracted metadata from such a malformed PDF. Versions prior to 2.10.5 throw an error, but do not hang forever. This issue was fixed with https://github.com/py-pdf/pypdf/pull/1331 which has been included in release 2.10.6. Users are advised to upgrade. Users unable to upgrade should modify `PyPDF2/generic/_data_structures.py::read_object` to an an error throwing case. See GHSA-hm9v-vj3r-r55m for details.

CVSS 3.1 · 6.2 Medium EPSS < 1% KEV · Not listed

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Py-pdf Pypdf Project

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Pypdf Pypdf

CVE-2023-36810

Quadratic runtime with malformed PDF missing xref marker in pypdf

pypdf is a pure-python PDF library capable of splitting, merging, cropping, and transforming the pages of PDF files. An attacker who uses this vulnerability can craft a PDF which leads to unexpected long runtime. This quadratic runtime blocks the current process and can utilize a single core of the CPU by 100%. It does not affect memory usage. This issue has been addressed in PR 808 and versions from 1.27.9 include this fix. Users are advised to upgrade. There are no known workarounds for this vulnerability.

CVSS 3.1 · 6.2 Medium EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2023-46250

pypdf possible Infinite Loop when PdfWriter(clone_from) is used with a PDF

pypdf is a free and open-source pure-python PDF library. An attacker who uses a vulnerability present in versions 3.7.0 through 3.16.4 can craft a PDF which leads to an infinite loop. This infinite loop blocks the current process and can utilize a single core of the CPU by 100%. It does not affect memory usage. That is, for example, the case when the pypdf-user manipulates an incoming malicious PDF e.g. by merging it with another PDF or by adding annotations. The issue was fixed in version 3.17.0. As a workaround, apply the patch manually by modifying `pypdf/generic/_data_structures.py`.

CVSS 3.1 · 5.1 Medium EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2025-62707

pypdf affected by possible infinite loop when reading DCT inline images without EOF marker

pypdf is a free and open-source pure-python PDF library. Prior to version 6.1.3, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires parsing the content stream of a page which has an inline image using the DCTDecode filter. This has been fixed in pypdf version 6.1.3.

CVSS 4.0 · 6.6 Medium EPSS < 1% KEV · Not listed

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Py-pdf Pypdf Project

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Pypdf Pypdf

CVE-2025-62708

pypdf manipulated LZWDecode streams can exhaust RAM

pypdf is a free and open-source pure-python PDF library. Prior to version 6.1.3, an attacker who uses this vulnerability can craft a PDF which leads to large memory usage. This requires parsing the content stream of a page using the LZWDecode filter. This has been fixed in pypdf version 6.1.3.

CVSS 4.0 · 6.6 Medium EPSS < 1% KEV · Not listed

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Py-pdf Pypdf Project

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Pypdf Pypdf

CVE-2026-103000

pypdf: Possible large memory usage when retrieving alphabetical page labels

pypdf is a free and open-source pure-python PDF library. Prior to 6.19.0, a crafted PDF can provide unusually large alphabetical page-label values that cause pypdf/_page_labels.py to generate strings beyond a reasonable page-label length when an application retrieves document page labels, consuming excessive memory and potentially making the application unavailable. This issue is fixed in version 6.19.0.

CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf

CVE-2026-102993

pypdf: Possible large memory usage when retrieving Roman page labels

pypdf is a free and open-source pure-python PDF library. Prior to 6.17.0, a crafted PDF can provide unusually large Roman page-label values that cause pypdf/_page_labels.py to generate excessively large numeral strings when an application retrieves document page labels, consuming large amounts of memory and potentially making the application unavailable. This issue is fixed in version 6.17.0.

CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed

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Py-pdf

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Pypdf