CVE-2026-27888
Published: 26 February 2026
Summary
CVE-2026-27888 is a high-severity Uncontrolled Resource Consumption (CWE-400) vulnerability in Pypdf Project Pypdf. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 17.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
Threat & Defense at a Glance
Threat & Defense Details
Likely Mitigating ControlsAI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Limiting concurrent sessions directly prevents uncontrolled resource consumption by capping the number of active sessions per user or account.
Analysis identifies uncontrolled resource consumption indicative of denial-of-service or abuse attempts.
Contingency plan testing includes resource exhaustion scenarios to verify recovery, making it harder for attackers to sustain exploits that cause uncontrolled consumption.
Updated contingency plans include current procedures to detect, contain, and recover from resource exhaustion, limiting an attacker's ability to sustain impact from uncontrolled consumption.
Alternate site allows resumption of operations if resource exhaustion at the primary site is exploited to cause unavailability.
Alternate telecommunications services enable resumption of essential functions when primary services become unavailable due to uncontrolled resource consumption.
The team can analyze and respond to resource exhaustion incidents, reducing the impact of attacks that exploit uncontrolled consumption weaknesses.
Timely maintenance support and spare parts enable rapid recovery from failures induced by uncontrolled resource consumption, shortening the impact window of denial-of-service attacks.
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).
NVD Description
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.
Deeper analysisAI
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.
Details
- CWE(s)