Denial of Service (DoS) Affecting pypdf package, versions [,6.21.2)

pypdf is an A pure-python PDF library capable of splitting, merging, cropping, and transforming PDF files

Affected versions of this package are vulnerable to Denial of Service (DoS) via repeated full file reads triggered by malformed PDF input. When get_object in pypdf/_reader.py encounters an invalid or unresolvable indirect object reference, it falls back to scanning the entire file stream on every lookup for that object rather than caching the failed resolution. Similarly, _read_standard_xref_table re-reads the full stream buffer on each cross-reference recovery attempt. An attacker can supply a PDF containing invalid objects or a corrupt cross-reference table to cause unbounded repeated full-file I/O, crashing or hanging the process.

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

• High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

• Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package

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