Security readout for executives and security teams
Plain-English summary
CVE-2026-28351 affects pypdf, a Python library used to process PDFs. A specially crafted PDF can cause excessive memory use when RunLengthDecode content streams are parsed. The main business risk is service slowdown or denial of service in systems that accept or process untrusted PDFs. The issue is fixed in pypdf 6.7.4.
Executive priority
Prioritize remediation for internet-facing or business-critical systems that process uploaded or external PDFs. This is not described as code execution, but it can affect availability. Upgrade during the next urgent dependency maintenance window, faster for high-volume PDF processing services.
Technical view
pypdf versions before 6.7.4 are vulnerable to CWE-400 resource exhaustion. The advisory describes manipulated RunLengthDecode streams causing large RAM consumption during content stream parsing. CVSS v4.0 is 6.9 with network attack vector, low complexity, no privileges, and no user interaction. Availability impact is rated low in the supplied vector.
Likely exposure
Exposure is most likely in applications, pipelines, or services using pypdf before 6.7.4 to parse PDFs from users, partners, email, uploads, archives, or other untrusted sources. Systems that only process trusted PDFs have lower practical exposure.
Exploitation context
The sources do not report active exploitation, and CISA KEV status is false in the provided bundle. Exploitation requires a crafted PDF and code paths that parse the content stream using the RunLengthDecode filter. The expected impact is memory exhaustion rather than data theft or code execution.
Researcher notes
The public record identifies the vulnerable component, fixed version, CWE, CVSS vector, advisory, PR, commit, and release. The supplied sources do not provide evidence of exploitation in the wild. Avoid assuming broader PDF tooling impact beyond pypdf before 6.7.4.
Mitigation direction
- Upgrade pypdf to version 6.7.4 or later.
- If immediate upgrade is not possible, review PR #3664 as the stated workaround basis.
- Limit processing of untrusted PDFs where pypdf cannot be updated promptly.
- Apply resource limits around PDF processing workloads where operationally feasible.
- Monitor vendor advisory and release notes for any updated guidance.
Validation and detection
- Inventory applications and services that include pypdf.
- Confirm deployed pypdf versions are 6.7.4 or later.
- Identify workflows that parse PDFs from untrusted sources.
- Review dependency lockfiles and container images for older pypdf versions.
- Check whether RunLengthDecode content stream parsing is reachable in affected workflows.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-400: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-28351 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.9 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
6.9MediumVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/py-pdf/pypdf/security/advisories/GHSA-f2v5-7jq9-h8cgCVE reference · x_refsource_CONFIRM
- https://github.com/py-pdf/pypdf/pull/3664CVE reference · x_refsource_MISC
- https://github.com/py-pdf/pypdf/commit/f309c6003746414dc7b5048c19e6d879ff2dc858CVE reference · x_refsource_MISC
- https://github.com/py-pdf/pypdf/releases/tag/6.7.4CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Uncontrolled Resource Consumption
Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.