pypdf: Possible infinite loop when hitting EOF in standard xref table during trailer search
Only affects pypdf when it opens an incomplete PDF with no trailer, where it can enter an infinite loop. The fix is in pypdf 6.21.4.
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Fix
- Fixed in 6.21.4
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: no
- Technical impact: partial
Summary
The pypdf Python library for reading and processing PDF files is affected. A specially crafted, incomplete PDF file can cause pypdf to hang indefinitely while it is being opened, which blocks the program's processing thread.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original description
pypdf is a free and open-source pure-python PDF library. Prior to 6.21.4, pypdf can enter an infinite loop while opening a crafted incomplete PDF whose standard cross-reference table reaches the end of the file without a trailer. The trailer search can repeatedly rewind to the same stream position instead of terminating when parsing makes no progress, blocking the processing thread. This issue is fixed in version 6.21.4.
Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: partial
- Record last updated
Affected versions
- py-pdf pypdf
fixed in 6.21.4
References 4
GitHub · py-pdf/pypdf
Questions about CVE-2026-119203
What does this mean?
When pypdf opens a PDF that is incomplete and has no trailer, its search for the trailer in the standard cross-reference table can run without end when it reaches end of file. The result is a denial of service, where pypdf stops responding.Source: github.com
Am I affected, and how do I check?
Versions of pypdf before 6.21.4 are affected, and the bug only triggers when the file being opened is incomplete and has no trailer. To check, compare the installed pypdf version against 6.21.4.Source: github.com
What should I do about it?
Upgrade pypdf to 6.21.4 or later, which contains the fix. If you cannot upgrade yet, apply the changes from PR #4289.Source: github.com
Is it being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data