#1153009 pxelinux: delayed TFTP replies can abort a later file request

Package:
syslinux
Source:
syslinux
Description:
collection of bootloaders (DOS FAT and NTFS bootloader)
Submitter:
Gianluigi Tiesi
Date:
2026-11-04 11:45:02 UTC
Severity:
normal
Tags:
#1153009#5
Date:
2026-11-04 11:43:20 UTC
From:
To:
lpxelinux's UDP allocator immediately reuses a closed socket's port.
A delayed TFTP error for a missing config can then reach a later request,
causing an existing config to be treated as missing.

Reproduced in QEMU by delaying a missing-file error until the request for
pxelinux.cfg/default. Keeping an allocator cursor avoids the collision;
the same test then loads default successfully. Allocation also handles
occupied ports, wraparound and exhaustion.

Patch: 0022-lpxelinux-rotate-udp-ports.patch
AI assistance was used for debugging, the patch and this report.