CVE-2026-27888
Published: 26 February 2026
Summary
CVE-2026-27888 is a medium-severity Uncontrolled Resource Consumption (CWE-400) vulnerability in Pypdf Project Pypdf. Its CVSS base score is 6.6 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 17.5th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SC-5 (Denial-of-service Protection) and SC-6 (Resource Availability).
Deeper analysis
CVE-2026-27888 is a denial-of-service vulnerability in pypdf, a free and open-source pure-Python PDF library. Versions prior to 6.7.3 are affected, where accessing the `xfa` property of a reader or writer object on a PDF with a stream compressed using `/FlateDecode` can lead to RAM exhaustion. The issue is classified under CWE-400 (Uncontrolled Resource Consumption) with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
An unauthenticated attacker (PR:N) can exploit this remotely (AV:N) with low complexity (AC:L) and no user interaction (UI:N) by crafting a malicious PDF file. Upon processing the file and accessing the vulnerable `xfa` property, the library exhausts available RAM, resulting in high-impact availability disruption (A:H) without affecting confidentiality or integrity.
The vulnerability has been fixed in pypdf version 6.7.3. Mitigation involves upgrading to this version, with a manual patch available as a workaround. Relevant advisories and resources include the GitHub security advisory (GHSA-x7hp-r3qg-r3cj), the fixing commit (7a4c8246ed48d9d328fb596942271da47b6d109c), pull request #3658, and the release notes for v6.7.3.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8791
Vulnerability details
pypdf is a free and open-source pure-python PDF library. Prior to 6.7.3, an attacker who uses this vulnerability can craft a PDF which leads to the RAM being exhausted. This requires accessing the `xfa` property of a reader or writer…
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and the corresponding stream being compressed using `/FlateDecode`. This has been fixed in pypdf 6.7.3. As a workaround, apply the patch manually.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
CVE describes remote (AV:N) exploitation of a public-facing application/library via malicious PDF input to trigger application-level resource exhaustion DoS (CWE-400).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Requires timely identification, reporting, and correction of flaws, directly addressing the RAM exhaustion vulnerability by mandating upgrades to pypdf 6.7.3 or application of the patch.
Protects system resources such as RAM from unauthorized consumption, comprehensively mitigating the uncontrolled resource exhaustion triggered by accessing the xfa property on malicious PDFs.
Employs controls to protect against denial-of-service attacks, including the high-impact availability disruption from remotely crafted PDFs exploiting pypdf.