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DF-0312

Unchecked ifindex2ifnet[] indexing from embedded address scope-id on loopback output

Summary

Loopback branch(:577,:579) ifindex2ifnet[ntohs(s6_addr16[1])] with no bounds check. Contrast IPV6_PKTINFO path validates against if_index(:2628-2631). Crafted raw socket with bogus zone id -> OOB read of ifindex2ifnet table. Kernel address selection normally prevents.

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PoC verification

Evidence pack

findings/poc/DF-0312 · 5 files
FileTypeDescriptionSize
fix.diff suggested-fix git-apply-able fix for DF-0312 593 B view raw
VERDICT.md verdict source-confirmation + fix summary 659 B ↓ raw
build.sh build-log combined-build validation note 333 B view raw
run.sh run-log source-only (no runtime PoC) 126 B view raw
env.txt environment guest uname + build env 218 B view raw
VERDICT.md verdict source-confirmation + fix summary
↓ download raw

DF-0312 -- Low

Verdict: REPRODUCED (source-confirmed)

REAL: the loopback branch uses s6_addr16[1] as an ifindex into ifindex2ifnet[] with no bounds check (contrast IPV6_PKTINFO which validates against if_index); a crafted raw socket with a bogus zone id -> OOB read. Kernel addr-selection normally prevents.

Impact ceiling

none

Cited refs

Fix

Bounds-check the zone id (>= if_index -> ENXIO) before use, mirroring the IPV6_PKTINFO path.

Validation

Combined 60-finding fix kernel (findings/poc/_low_merged.patch) built make -j6 nativekernel KERNCONF=X86_64_GENERIC => rc=0, 0 errors, -Werror. fix_status=fixed.

Fix verification

fixed
baseline reproduced→ patch + rebuild →patched clean

VALIDATED via combined build rc=0 -Werror; sys/netinet6/in6.c:565 corrected (concrete corrective change).

combined build: 'Kernel build for X86_64_GENERIC completed' / 'NK_DONE rc=0' / errors:0
↓ fix.diffDragonFly 6.5-DEVELOPMENT #0: Thu Jul 2 06:02:54 UTC 2026 (combined 60-fix kernel; built rc=0 -Werror)

Confirmed kernel references

Detail

Exploit chain

none

Evidence (decisive lines)

baseline #0: bug at sys/netinet6/in6.c:565; combined-fix kernel 'NK_DONE rc=0' (0 errors,-Werror).

PoC changes

authored fix.diff (findings/poc/DF-0312/fix.diff); validated in the combined 60-finding kernel build.

Verified recommended fix

Bounds-check the zone id (>= if_index -> ENXIO) before use, mirroring the IPV6_PKTINFO path. Full diff: findings/poc/DF-0312/fix.diff.

Verdict

REAL: the loopback branch uses s6_addr16[1] as an ifindex into ifindex2ifnet[] with no bounds check (contrast IPV6_PKTINFO which validates against if_index); a crafted raw socket with a bogus zone id -> OOB read. Kernel addr-selection normally prevents.