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sys/net/dhcpv6: reject truncated option headers [backport 2026.10] - #23034
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crasbe merged 1 commit intoOct 29, 2026
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Assisted-by: DeepSeek v4.1 Flash 1017 (cherry picked from commit d493a4c)
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Backport of #23018
Contribution description
The DHCPv6 option walker reads a four byte option header without checking that four bytes remain. A message with one to three trailing bytes after its last complete option makes the parser read past the end of the message.
The real recv_buf is 256 bytes and is followed by best_adv, so the read lands in valid static memory on normal builds. It reads one or two bytes only, and the values are used for parsing, never sent back to the attacker. There is no write, no code execution, and no reliable crash.
Testing procedure
Issues/PRs references
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