jffs2: fix use-after-free in jffs2_clear_xattr_subsystem

Description

In the Linux kernel, the following vulnerability has been resolved: jffs2: fix use-after-free in jffs2_clear_xattr_subsystem When we mount a jffs2 image, assume that the first few blocks of the image are normal and contain at least one xattr-related inode, but the next block is abnormal. As a result, an error is returned in jffs2_scan_eraseblock(). jffs2_clear_xattr_subsystem() is then called in jffs2_build_filesystem() and then again in jffs2_do_fill_super(). Finally we can observe the following report: ================================================================== BUG: KASAN: use-after-free in jffs2_clear_xattr_subsystem+0x95/0x6ac Read of size 8 at addr ffff8881243384e0 by task mount/719 Call Trace: dump_stack+0x115/0x16b jffs2_clear_xattr_subsystem+0x95/0x6ac jffs2_do_fill_super+0x84f/0xc30 jffs2_fill_super+0x2ea/0x4c0 mtd_get_sb+0x254/0x400 mtd_get_sb_by_nr+0x4f/0xd0 get_tree_mtd+0x498/0x840 jffs2_get_tree+0x25/0x30 vfs_get_tree+0x8d/0x2e0 path_mount+0x50f/0x1e50 do_mount+0x107/0x130 __se_sys_mount+0x1c5/0x2f0 __x64_sys_mount+0xc7/0x160 do_syscall_64+0x45/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Allocated by task 719: kasan_save_stack+0x23/0x60 __kasan_kmalloc.constprop.0+0x10b/0x120 kasan_slab_alloc+0x12/0x20 kmem_cache_alloc+0x1c0/0x870 jffs2_alloc_xattr_ref+0x2f/0xa0 jffs2_scan_medium.cold+0x3713/0x4794 jffs2_do_mount_fs.cold+0xa7/0x2253 jffs2_do_fill_super+0x383/0xc30 jffs2_fill_super+0x2ea/0x4c0 [...] Freed by task 719: kmem_cache_free+0xcc/0x7b0 jffs2_free_xattr_ref+0x78/0x98 jffs2_clear_xattr_subsystem+0xa1/0x6ac jffs2_do_mount_fs.cold+0x5e6/0x2253 jffs2_do_fill_super+0x383/0xc30 jffs2_fill_super+0x2ea/0x4c0 [...] The buggy address belongs to the object at ffff8881243384b8 which belongs to the cache jffs2_xattr_ref of size 48 The buggy address is located 40 bytes inside of 48-byte region [ffff8881243384b8, ffff8881243384e8) [...] ================================================================== The triggering of the BUG is shown in the following stack: ----------------------------------------------------------- jffs2_fill_super jffs2_do_fill_super jffs2_do_mount_fs jffs2_build_filesystem jffs2_scan_medium jffs2_scan_eraseblock <--- ERROR jffs2_clear_xattr_subsystem <--- free jffs2_clear_xattr_subsystem <--- free again ----------------------------------------------------------- An error is returned in jffs2_do_mount_fs(). If the error is returned by jffs2_sum_init(), the jffs2_clear_xattr_subsystem() does not need to be executed. If the error is returned by jffs2_build_filesystem(), the jffs2_clear_xattr_subsystem() also does not need to be executed again. So move jffs2_clear_xattr_subsystem() from 'out_inohash' to 'out_root' to fix this UAF problem.

Scores

EPSS (exploitation in 30 days)

0.26% · top 82% of all CVEs (6 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: total

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.

Weakness

• CWE-416 Use After Free (opens in a new tab)All about CWE-416 and its CVEs

Affected products

• Linux · Linux

  • affected aa98d7cf59b5b0764d3502662053489585faf2fe – < 9150cb625b46f68d524f4cfd491f1aafc23e10a9
  • affected aa98d7cf59b5b0764d3502662053489585faf2fe – < 3bd2454162ec6bbb5503233c804fce6e4b6dcec5
  • affected aa98d7cf59b5b0764d3502662053489585faf2fe – < c3b07c875fa8f906f932976460fd14798596f101
  • affected aa98d7cf59b5b0764d3502662053489585faf2fe – < 30bf7244acf32f19cb722c39f7bc1c2a9f300422
  • affected aa98d7cf59b5b0764d3502662053489585faf2fe – < 7bb7428dd73991bf4b3a7a61b493ca50046c2b13
  • affected aa98d7cf59b5b0764d3502662053489585faf2fe – < 7a75740206af5f17e9f3efa384211cba70213da1
  • affected aa98d7cf59b5b0764d3502662053489585faf2fe – < 22327bd7988f21de3a53c1373f3b81542bfe1f44
  • affected aa98d7cf59b5b0764d3502662053489585faf2fe – < 8c0f024f29e055840a5a89fe23b96ae3f921afed
  • affected aa98d7cf59b5b0764d3502662053489585faf2fe – < 4c7c44ee1650677fbe89d86edbad9497b7679b5c

• Linux · Linux

  • affected 2.6.18
  • unaffected < 2.6.18
  • unaffected 4.9.311 – ≤ 4.9.*
  • unaffected 4.14.276 – ≤ 4.14.*
  • unaffected 4.19.238 – ≤ 4.19.*
  • unaffected 5.4.189 – ≤ 5.4.*
  • unaffected 5.10.110 – ≤ 5.10.*
  • unaffected 5.15.33 – ≤ 5.15.*
  • unaffected 5.16.19 – ≤ 5.16.*
  • unaffected 5.17.2 – ≤ 5.17.*
  • unaffected 5.18 – ≤ *

References (9)

• https://git.kernel.org/stable/c/9150cb625b46f68d524f4cfd491f1aafc23e10a9 (opens in a new tab)
• https://git.kernel.org/stable/c/3bd2454162ec6bbb5503233c804fce6e4b6dcec5 (opens in a new tab)
• https://git.kernel.org/stable/c/c3b07c875fa8f906f932976460fd14798596f101 (opens in a new tab)
• https://git.kernel.org/stable/c/30bf7244acf32f19cb722c39f7bc1c2a9f300422 (opens in a new tab)
• https://git.kernel.org/stable/c/7bb7428dd73991bf4b3a7a61b493ca50046c2b13 (opens in a new tab)
• https://git.kernel.org/stable/c/7a75740206af5f17e9f3efa384211cba70213da1 (opens in a new tab)
• https://git.kernel.org/stable/c/22327bd7988f21de3a53c1373f3b81542bfe1f44 (opens in a new tab)
• https://git.kernel.org/stable/c/8c0f024f29e055840a5a89fe23b96ae3f921afed (opens in a new tab)
• https://git.kernel.org/stable/c/4c7c44ee1650677fbe89d86edbad9497b7679b5c (opens in a new tab)

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2021-47656](https://trackcve.app/badge/CVE-2021-47656.svg)](https://trackcve.app/cve/CVE-2021-47656)

Record last updated 5 Aug 2026, 08:48 UTC.