pypdf is a free and open-source pure-python PDF library. Prior to 6.21.3, pypdf can consume excessive time and memory when an application accesses the page count of a crafted encrypted PDF whose page tree declares a forged /Count value. Even after successful decryption, page-count retrieval trusts the unvalidated declared count instead of walking the page tree, allowing the attacker-controlled value to drive excessive work and memory use. This issue is fixed in version 6.21.3.
CVSS Score
7.1
EPSS Score
0.003
Published
2026-10-29
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 Score
7.1
EPSS Score
0.003
Published
2026-10-29
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 Score
7.1
EPSS Score
0.003
Published
2026-10-29
pypdf is a free and open-source pure-python PDF library. Prior to 6.21.4, pypdf can consume excessive memory while parsing a crafted PDF page tree containing many shared resources. Page-tree flattening copies page dictionary and inherited resource entries without a document-wide entry budget, allowing the crafted resource structure to cause disproportionate allocations. This issue is fixed in version 6.21.4.
CVSS Score
7.1
EPSS Score
0.003
Published
2026-10-29
pypdf is a free and open-source pure-python PDF library. Prior to 6.21.4, pypdf can enter an infinite loop when cloning or duplicating a crafted cyclic DictionaryObject. Clone traversal checked generated destination references rather than the original source references, allowing some source cycles to evade the visited-object check. This issue is fixed in version 6.21.4.
CVSS Score
7.1
EPSS Score
0.003
Published
2026-10-29
pypdf is a free and open-source pure-python PDF library. Prior to 6.21.3, pypdf can consume excessive memory when strict mode loads a crafted invalid PDF dictionary. Nested parsing failures add repeated exception text to newly raised errors, allowing a small malformed dictionary to amplify into very large error messages. This issue is fixed in version 6.21.3.
CVSS Score
7.1
EPSS Score
0.003
Published
2026-10-29
pypdf is a free and open-source pure-python PDF library. Prior to 6.21.3, pypdf can take excessive time to retrieve page labels from a crafted PDF containing a flat page-label number tree with many ranges. The page_labels property resolves each page independently and repeatedly scans the same /Nums array from the beginning, causing work to grow with both the page count and the number of label ranges. This issue is fixed in version 6.21.3.
CVSS Score
7.1
EPSS Score
0.002
Published
2026-10-29
pypdf is a free and open-source pure-python PDF library. Prior to 6.20.0, an attacker can craft an incomplete PDF that ends inside a standard cross-reference table, causing pypdf to mishandle the unexpected end of file and enter an infinite loop. This issue is fixed in version 6.20.0.
CVSS Score
6.0
EPSS Score
0.005
Published
2026-10-21
pypdf is a free and open-source pure-python PDF library. Prior to 6.20.0, accessing a crafted PDF stream with a large number of filters or multiple filters that pass around large amounts of data can cause large memory consumption. This issue is fixed in version 6.20.0.
CVSS Score
6.0
EPSS Score
0.005
Published
2026-10-21
pypdf is a free and open-source pure-python PDF library. Prior to 6.21.0, an attacker can craft a PDF containing a content stream with many small operations, causing parsing to consume large amounts of memory. This issue is fixed in version 6.21.0.
CVSS Score
6.0
EPSS Score
0.004
Published
2026-10-21
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