CVE-2026-84310: pypdf · Possible long runtimes/large memory usage when retrieving outlines
Affects pdflySource GCVE Database
Not known to be exploited · CVSS 4.8 Medium : upgrade to 0.5.1_25 when convenient.
Data as of 26 Oct 2026, 18:58 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 0.5.1_25
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 1 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade pdfly to 0.5.1_25.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewpdflypkg:brew/pdflyOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
### Impact An attacker who uses this vulnerability can craft a PDF which leads to long runtimes and large memory consumption. This requires accessing the outlines of a document with either lots of entries or nested outlines with long re-used nesting paths. ### Patches This has been fixed in [pypdf==6.16.1](https://github.com/py-pdf/pypdf/releases/tag/6.16.1). ### Workarounds If you cannot upgrade yet, consider applying the changes from PR [#3966](https://github.com/py-pdf/pypdf/pull/3966).
References
- github.com/py-pdf/pypdf/security/advisories/GHSA-23w6-3w8w-8484 (opens in a new tab)
- github.com/py-pdf/pypdf/pull/3966 (opens in a new tab)
- github.com/py-pdf/pypdf/commit/d91ab705fd81ed1a9cec175c6958600dea1a4942 (opens in a new tab)
- github.com/py-pdf/pypdf (opens in a new tab)
- github.com/py-pdf/pypdf/releases/tag/6.16.1 (opens in a new tab)