# CVE-2026-74560: xsk: fix buffer leak in xsk_drop_skb() for AF_XDP multi-buffer Tx CVE-2026-74560 is fixed in 20 products on 1 platform, first by DEBIAN-CVE-2026-74560, released August 16, 2026. It is not reported as exploited. Patch Radar priority: Routine. - Web page: https://patchblox.com/security/cve/CVE-2026-74560 - Priority: Routine - CVSS: 3.3 (Low) - EPSS: 0.0016 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Aug 15, 2026 - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-74560 ## Description In the Linux kernel, the following vulnerability has been resolved: xsk: fix buffer leak in xsk_drop_skb() for AF_XDP multi-buffer Tx This patch is inspired by the check[1] from sashiko. It says when overflow happens, the address of cq to be published is invalid. Actually the severer thing is the whole process of publishing the address of cq in this particular case is not right: it should truely publish the address and advance the cached_prod in cq as long as it reads descriptors from txq. The following is the full analysis. xsk_drop_skb() is called in three places, which all discard a partially built multi-buffer skb: 1) xsk_build_skb() -EOVERFLOW error path: packet exceeds MAX_SKB_FRAGS 2) __xsk_generic_xmit() post-loop cleanup: an invalid descriptor in the TX ring prevents the partial packet from completing 3) xsk_release(): socket close while xs->skb holds an incomplete packet In all three cases, the TX descriptors for the already-processed frags have been consumed from the TX ring (xskq_cons_release), and CQ slots have been reserved. However, xsk_drop_skb() calls xsk_consume_skb() which cancels the CQ reservations via xsk_cq_cancel_locked(). Since the buffer addresses never appear in the completion queue, userspace permanently loses track of these buffers. Fix this by letting consume_skb() trigger the existing xsk_destruct_skb destructor, which already submits buffer addresses to the CQ via xsk_cq_submit_addr_locked(). Note that cancelling the descriptors back to the TX ring (via xskq_cons_cancel_n) is not a appropriate option because an oversized packet that always exceeds MAX_SKB_FRAGS would be retried indefinitely, which is an obviously deadlock bug in the TX path. Also move the desc->addr assignment in xsk_build_skb() above the overflow check so that the current descriptor's address is recorded before a potential -EOVERFLOW jump to free_err, consistent with the zerocopy path in xsk_build_skb_zerocopy(). [1]: https://lore.kernel.org/all/20260425041726.85FB3C2BCB2@smtp.kernel.org/ ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | bpftool6.18 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | bpftool6.18-debuginfo amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel-livepatch-6.18.44-99.149 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-debuginfo amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-debuginfo-common-aarch64 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-debuginfo-common-x86_64 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-devel amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-headers amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-modules-extra amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-modules-extra-common amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-tools amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-tools-debuginfo amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-tools-devel amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | linux Debian 14 | 7.1.8-1 | [DEBIAN-CVE-2026-74560](https://patchblox.com/security/data/fix/linux/debian-cve-2026-74560.md) | Aug 16, 2026 | | Linux | microvm-kernel6.18 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | perf6.18 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | perf6.18-debuginfo amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | python3-perf6.18 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | python3-perf6.18-debuginfo amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | --- Data as of 2026-11-09T01:18:40Z UTC. 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