security: cherry-pick CVE-2026-21869 (n_discard heap-buffer-overflow in server)#122
Merged
TheTom merged 1 commit intofeature/turboquant-kv-cachefrom May 4, 2026
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…869) (ggml-org#22267) * server: clamp n_discard to non-negative at JSON parse boundary (CVE-2026-21869) A negative n_discard from client JSON causes heap-buffer-overflow in update_slots() context-shift loop (CWE-787, CVSS 8.8). Clamp to 0 at ingress; n_discard=0 already triggers auto-discard (n_left/2). Ref: GHSA-8947-pfff-2f3c * cont : cleaner * cont : cleanerer * cont : cleanest --------- Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
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Summary
Cherry-picks the upstream fix for CVE-2026-21869 (CVSS 8.8 HIGH).
A negative
n_discardfrom client JSON causes heap-buffer-overflow in theupdate_slots()context-shift loop (CWE-787). One-line clamp at the JSON parse boundary intools/server/server-task.cpp.Upstream commit: ggml-org/llama.cpp@c78fb909b (PR ggml-org#22267, merged Apr 23 2026, by @SongLi-arm and @ggerganov).
Impact
Affects anyone running
llama-serverfrom this fork. Single malformed JSON request crashes the server with a heap corruption. Trivially exploitable; no auth required if the server is reachable.Changes
tools/server/server-task.cpp— one-line clampn_discard = std::max(n_discard, 0)at JSON parse.Test plan
llama-servertarget (M5 Max, macOS 26): clean compile, binary launches normally{"n_discard": -1}to confirm the fix landsRecommend merging quickly given the CVSS rating.
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