pypdf: manipulated stream length values can exhaust RAM
### Impact An attacker who uses this vulnerability can craft a PDF which leads to large memory usage. This requires parsing a content stream with a rather large `/Length` value, regardless of the actual data length inside the stream. ### Patches This has been fixed in [pypdf==6.8.0](https://github.com/py-pdf/pypdf/releases/tag/6.8.0). ### Workarounds If you cannot upgrade yet, consider applying the changes from PR [#3675](https://github.com/py-pdf/pypdf/pull/3675). As far as we are aware, this mostly affects reading from buffers of unknown size, as returned by `open("file.pdf", mode="rb")` for example. Passing a file path or a `BytesIO` buffer to *pypdf* instead does not seem to trigger the vulnerability.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-31826US | medium5.5 | — | ||
pypdf is a free and open-source pure-python PDF library. Prior to 6.8.0, an attacker who uses this vulnerability can craft a PDF which leads to large memory usage. This requires pa… | ||||
references
External citations — patches, advisories, analysis.
- https://github.com/advisories/GHSA-hqmh-ppp3-xvm7ADVISORY
- https://github.com/py-pdf/pypdfPACKAGE
- https://github.com/py-pdf/pypdf/commit/3c550b3196adeba1506a26e57c09c09fac75e9aaWEB
- https://github.com/py-pdf/pypdf/pull/3675WEB
- https://github.com/py-pdf/pypdf/releases/tag/6.8.0WEB
- https://github.com/py-pdf/pypdf/security/advisories/GHSA-hqmh-ppp3-xvm7WEB
- https://nvd.nist.gov/vuln/detail/CVE-2026-31826ADVISORY
- https://pypi.org/project/pypdfPACKAGE
Advisories like this name the exposed products attackers go after on your perimeter. See what is exposed on your perimeter with a free passive scan.
Free scan