pypdf: manipulated stream length values can exhaust RAM

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.8 · CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-31826: 0.18% estimated exploitation activity in the next 30 days; percentile 7.92 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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. Workarounds If you cannot upgrade yet, consider applying the changes from PR #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.

Published by the source

11 Mar 2026, 00:14 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 13:37 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-hqmh-ppp3-xvm7

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-hqmh-ppp3-xvm7

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# Patch Next advisory brief: CVE-2026-31826

Advisory: pypdf: manipulated stream length values can exhaust RAM
IDs: CVE-2026-31826, GHSA-hqmh-ppp3-xvm7
Record: https://patchnext.com/advisories/cve-2026-31826 (revision 3, source checked 26 Oct 2026, 13:37 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: pypdf 6.8.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI pypdf: affected < 6.8.0; fixed in 6.8.0

## Suggested inspection (read-only)
- `python -m pip show pypdf`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on pypdf.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-hqmh-ppp3-xvm7 (OSV record GHSA-hqmh-ppp3-xvm7 lists affected ranges: PyPI pypdf >=0 <6.8.0 (fixed))
- Verified: https://github.com/advisories/GHSA-hqmh-ppp3-xvm7 (GitHub-reviewed advisory GHSA-hqmh-ppp3-xvm7 lists affected ranges: PyPI pypdf >=0 <6.8.0)

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