VulnerabilityPublished 25 Feb 2026Updated 27 Feb 2026

CVE-2026-27628: py-pdf pypdf · Infinite Loop

Affects py-pdf pypdfSource CVE Database V5

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Not known to be exploited · CVSS 1.2 Low : upgrade to 6.7.2 when convenient.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 4.0 base score

1.2Low

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 33% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 6.7.2

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U

Base metrics

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: Active
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Threat metrics

Exploit Maturity: Unreported

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Active: Successful exploitation of this vulnerability requires a targeted user to perform specific, conscious interactions with the vulnerable system and the attacker’s payload, or the user’s interactions would actively subvert protection mechanisms which would lead to exploitation of the vulnerability.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
Exploit Maturity: Unreported: Based on threat intelligence sources each of the following must apply: · No knowledge of publicly available proof-of-concept · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 25 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade py-pdf pypdf to 6.7.2.

Affected software

Product	Affected	Fixed in
py-pdfpypdf	Affected <6.7.2	Fixed in 6.7.2
PyPIpypdf`pkg:pypi/pypdf`Other threats	Affected <6.7.2	Fixed in 6.7.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

The most effective mitigation is to upgrade pypdf to version 6.7.2 or later, where this vulnerability has been fixed. If upgrading is not immediately feasible, users should manually apply the patch provided by the pypdf maintainers to correct the infinite loop condition. Additionally, organizations should implement input validation and sandboxing for PDF processing to isolate and limit the impact of malicious files. Restricting PDF processing to trusted sources and scanning incoming PDFs with security tools can reduce exposure. Monitoring application performance and setting timeouts or resource limits on PDF parsing operations can help detect and mitigate hangs caused by infinite loops. Finally, educating users about the risks of opening untrusted PDFs and enforcing strict file upload policies can reduce the likelihood of exploitation.

Description

### Impact An attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires reading the file. ### Patches This has been fixed in [pypdf==6.7.2](https://github.com/py-pdf/pypdf/releases/tag/6.7.2). ### Workarounds If users cannot upgrade yet, consider applying the changes from PR [#3655](https://github.com/py-pdf/pypdf/pull/3655).

Impact

The primary impact of this vulnerability is denial of service through application hang or resource exhaustion caused by the infinite loop. Organizations that use pypdf to process PDFs—such as document management systems, automated PDF parsers, or web applications handling PDF uploads—may experience service disruptions or degraded performance when processing malicious PDFs. This can affect availability and potentially lead to operational downtime or degraded user experience. Since the vulnerability does not allow code execution or data leakage, confidentiality and integrity impacts are minimal. However, the disruption caused by the infinite loop can be exploited by attackers to target critical services that rely on pypdf, especially in automated workflows or batch processing environments. The lack of known exploits reduces immediate risk, but the ease of triggering the infinite loop by simply opening a crafted PDF means the threat should not be ignored.

Summary

CVE-2026-27628 identifies a vulnerability in the pypdf library, a pure-Python PDF processing tool widely used for reading and manipulating PDF files. The flaw is categorized under CWE-835, which involves a loop with an unreachable exit condition, effectively causing an infinite loop. In this case, an attacker can craft a malicious PDF file that triggers this infinite loop when parsed by vulnerable versions of pypdf (versions earlier than 6.7.2). The infinite loop occurs during the reading phase of the PDF, causing the application or service using pypdf to hang indefinitely, leading to denial of service (DoS). The attack vector requires the victim to open or process the crafted PDF, implying user interaction is necessary. No authentication or privileges are required to exploit this vulnerability. The CVSS 4.0 base score is 1.2, reflecting low severity due to limited impact and exploitation complexity. The vulnerability was publicly disclosed on February 25, 2026, and has been addressed in pypdf 6.7.2. While no known exploits have been reported in the wild, the vulnerability poses a risk to any system that automatically processes untrusted PDF files using vulnerable pypdf versions.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Mar 2026, 18:51 UTC

WeaknessesCWE-835

Technical details

References

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