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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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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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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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CVE-2026-102994

pypdf: Possible long runtimes/large memory usage when parsing indirect objects

pypdf is a free and open-source pure-python PDF library. Prior to 6.18.0, a crafted PDF containing indirect-object identifiers or generation-number tokens that continue for a long time without whitespace can cause pypdf/_reader.py and pypdf/generic/_base.py to scan excessive input through read_until_whitespace, resulting in long runtimes and application unavailability. This issue is fixed in version 6.18.0.

CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
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CVE-2026-102995

pypdf: Possible large memory usage for large /ToUnicode streams (Follow-up 2)

pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF can place unusually large source-code or destination-string tokens in a font /ToUnicode mapping, causing pypdf/_cmap.py parse_bfchar to decode and retain oversized values during operations such as text extraction and consume excessive memory. This is a second follow-up to earlier /ToUnicode resource-consumption fixes and is limited to the remaining token-length path. This issue is fixed in version 6.18.1.

CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
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CVE-2026-102996

pypdf: Possible large memory usage when parsing font data

pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF can provide a TrueType or Type1 simple font with an unusually large /Widths array, causing pypdf/_font.py Font._collect_tt_t1_character_widths to process entries beyond the 256 character codes meaningful for a simple font and consume excessive memory during operations such as text extraction. This issue is fixed in version 6.18.1.

CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
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CVE-2026-102997

pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)

pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filters.py to use inefficient byte-by-byte decompression while the earlier recovery counter fails to advance for bytes that successfully decode, causing long runtimes and application unavailability. This is a residual issue after the malformed FlateDecode recovery fix. This issue is fixed in version 6.18.1.

CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
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CVE-2026-102998

pypdf: Possible long runtimes when generating appearance streams

pypdf is a free and open-source pure-python PDF library. Prior to 6.19.0, a crafted PDF with form field values can cause pypdf/generic/_appearance_stream.py appearance-stream generation to repeat invariant selection-data work inside a loop when an application updates fields with flattening enabled, resulting in excessive runtimes and application unavailability. This issue is fixed in version 6.19.0.

CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
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CVE-2026-102999

pypdf: Possible long runtimes with large amount of embedded files

pypdf is a free and open-source pure-python PDF library. Prior to 6.19.0, a crafted PDF containing many embedded files can cause the dictionary-based attachments API in pypdf/_doc_common.py to reparse the full attachment list for each content lookup, producing repeated work and long runtimes when an application accesses the embedded-file mapping. This issue is fixed in version 6.19.0.

CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
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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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CVE-2026-119203

pypdf: Possible infinite loop when hitting EOF in standard xref table during trailer search

pypdf is a free and open-source pure-python PDF library. Prior to 6.21.4, pypdf can enter an infinite loop while opening a crafted incomplete PDF whose standard cross-reference table reaches the end of the file without a trailer. The trailer search can repeatedly rewind to the same stream position instead of terminating when parsing makes no progress, blocking the processing thread. This issue is fixed in version 6.21.4.

CVSS 4.0 · 7.1 High EPSS < 1% KEV · Not listed
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CVE-2026-119209

pypdf: Possible large memory usage when parsing cross-reference streams

pypdf is a free and open-source pure-python PDF library. Prior to 6.21.3, pypdf can consume excessive memory while opening a crafted PDF containing cross-reference streams that declare very large entry counts. Highly compressible streams and /Prev chains can multiply the number of parsed entries across a document, while negative /Index counts can bypass the existing per-stream clamp. This issue is fixed in version 6.21.3.

CVSS 4.0 · 7.1 High EPSS < 1% KEV · Not listed
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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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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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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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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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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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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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CVE-2026-41168

pypdf has possible long runtimes for wrong size values in cross-reference and object streams

pypdf is a free and open-source pure-python PDF library. An attacker who uses a vulnerability present in versions prior to 6.10.1 can craft a PDF which leads to long runtimes. This requires cross-reference streams with wrong large `/Size` values or object streams with wrong large `/N` values. This has been fixed in pypdf 6.10.1. As a workaround, one may apply the changes from the patch manually.

CVSS 4.0 · 6.9 Medium EPSS < 1% KEV · Not listed
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CVE-2026-48735

pypdf: Manipulated XMP metadata streams can exhaust RAM

pypdf is a free and open-source pure-python PDF library. Prior to 6.12.1, an attacker who uses this vulnerability can craft a PDF which leads to large memory usage. This requires parsing large XMP metadata, possibly with lots of unnecessary elements. This vulnerability is fixed in 6.12.1.

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