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VulnerabilityPublished Updated

CVE-2026-27026: py-pdf pypdf · Unthrottled Resource Allocation

Affects py-pdf pypdfSource CVE Database V5

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Not known to be exploited · CVSS 6.9 Medium : upgrade to 6.7.1 when convenient.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 4.0 base score
6.9Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 6.7.1
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 20 Feb 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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.

What to do

Upgrade py-pdf pypdf to 6.7.1.

Affected software

ProductAffectedFixed in
py-pdfpypdfAffected
  • <6.7.1
Fixed in
  • 6.7.1

AI-suggested

To mitigate CVE-2026-27026, organizations should upgrade all instances of pypdf to version 6.7.1 or later, where the vulnerability is fixed. If immediate upgrade is not feasible, implement strict input validation and sanitization to detect and reject malformed or suspicious PDF files, particularly those with unusual /FlateDecode streams. Employ resource monitoring and limits on CPU and memory usage for PDF processing tasks to prevent excessive resource consumption. Consider sandboxing PDF processing operations to isolate potential denial of service impacts. Additionally, restrict the sources of PDF files to trusted origins where possible and apply network-level controls to limit exposure. Regularly audit and update dependencies to ensure known vulnerabilities are patched promptly. Finally, monitor logs and system performance for anomalies indicative of exploitation attempts.

Description

### Impact 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. ### Patches This has been fixed in [pypdf==6.7.1](https://github.com/py-pdf/pypdf/releases/tag/6.7.1). ### Workarounds If you cannot upgrade yet, consider applying the changes from PR [#3644](https://github.com/py-pdf/pypdf/pull/3644).

References

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