Preliminary research
L3akCTF 2026 "Squid": racing `/proc/self/fd` symlinks against Flask `send_file`
L3akCTF 2026: Squid
AI-collected research leads through 22 September 2026, including targeted additions between broader sweeps. Unranked, incomplete, not community-vetted, and subject to change.
Solves a Flask file-disclosure challenge by racing recycled procfs file descriptors between stat and open. A regular file supplies a nonzero length before an environment file replaces it, bypassing response-length suppression for zero-size procfs entries without requiring attacker-controlled filesystem writes.
Record
- Document
- L3akCTF 2026: Squid
- Researcher
- Jorian Woltjer
- Published by
- Jorian Woltjer
- Topic
- Other
In the archive
Related sources
- ujson parser differential advisory Advisory
Tags
This page is the archive's own catalogue record. The research is the work of Jorian Woltjer, first published at the original source. Preserved copies are kept so the citation survives its host; this one was last captured on .