GHSA-4vqv-7265-gm2w CVE-2026-119207

pypdf has possible large memory usage for exceptions in strict mode

High PyPI

Severity: 7.1 / 10; High · CVSS 4.0
Exploit chance (EPSS): 0.30%; Chance of exploitation in the next 30 days. Higher than 23.19% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-400 Uncontrolled Resource Consumption; CWE-405 Asymmetric Resource Consumption (Amplification)
Fix: 6.21.3; Upgrade pypdf to this version or later

Description

Impact

An attacker who uses this vulnerability can craft a PDF which leads to large memory usage. This requires loading an invalid dictionary.

Patches

This has been fixed in pypdf==6.21.3.

Workarounds

If you cannot upgrade yet, consider applying the changes from PR #4265.

Affected versions

PyPI

Package	Vulnerable	Fixed in
pypdf	`< 6.21.3`	`6.21.3`
pypdf	`< 6.21.3`	`6.21.3`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

pypdf PyPI → `6.21.3`

pip

pip install --upgrade "pypdf>=6.21.3"

poetry

poetry add "pypdf>=6.21.3"

uv

uv add "pypdf>=6.21.3"

Severity breakdown

CVSS 4.0 7.1

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Attack vector: Network
Attack complexity: Low
Attack requirements: None
Privileges required: None
User interaction: Passive
Confidentiality (vulnerable system): None
Integrity (vulnerable system): None
Availability (vulnerable system): High
Confidentiality (subsequent systems): None
Integrity (subsequent systems): None
Availability (subsequent systems): None

Weakness

CWE-400: Uncontrolled Resource Consumption

The product does not properly control the allocation and maintenance of a limited resource.

How to prevent it

Architecture and Design: Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
Architecture and Design: Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed. The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question. The second solution is simply difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
Architecture and Design: Ensure that protocols have specific limits of scale placed on them.
Implementation: Ensure that all failures in resource allocation place the system into a safe posture.

CWE-405: Asymmetric Resource Consumption (Amplification)

The product does not properly control situations in which an adversary can cause the product to consume or produce excessive resources without requiring the adversary to invest equivalent work or otherwise prove authorization, i.e., the adversary's influence is "asymmetric."

How to prevent it

Architecture and Design: An application must make resources available to a client commensurate with the client's access level.
Architecture and Design: An application must, at all times, keep track of allocated resources and meter their usage appropriately.
System Configuration: Consider disabling resource-intensive algorithms on the server side, such as Diffie-Hellman key exchange.

References

Advisories

Fixes and patches

Packages

github.com/py-pdf/pypdf

Timeline

Oct 30, 2026 Published
Oct 30, 2026 Last updated by the source
Nov 1, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-5849-834g-hvw5 pypdf has possible infinite loop when hitting EOF in standard xref table during trailer search	High	Also affects pypdf
GHSA-cggf-277g-3q54 pypdf has possible large memory usage when parsing page tree	High	Also affects pypdf
GHSA-mfr5-77xh-9j7h pypdf has possible infinite loop when cloning dictionaries	High	Also affects pypdf
GHSA-42gh-23hr-vphw pypdf has possible long runtimes when retrieving page labels	High	Also affects pypdf
GHSA-62m5-6wh8-28x7 pypdf has possible long runtimes/large memory usage for encrypted PDF files	High	Also affects pypdf
GHSA-x3rh-gjgm-fmqc pypdf has possible large memory usage when parsing cross-reference streams	High	Also affects pypdf
GHSA-jr96-gvgh-j3r4 pypdf: Possible long runtimes for repeated malformed cross-reference entries (Follow-up)	High	Also affects pypdf
GHSA-gmh7-3g9r-mjh5 pypdf: Possible long runtimes for large xref table header limits	High	Also affects pypdf

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