CVE-2021-47637: ubifs: Fix deadlock in concurrent rename whiteout and inode writeback
Noroxi assessment
Priority: Monitor (action score 22/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.19% (FIRST EPSS).
- Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
- Fixed version: Linux Linux 37bdf1ad592555ecda1d55b89f6e393e4c0589d1, 70e9090acc32348cedc5def0cd6d5c126efc97b9, 83e42a78428fc354f5e2049935b84c8d8d29b787.
Low priority for now. Upgrade to Linux Linux 37bdf1ad592555ecda1d55b89f6e393e4c0589d1, 70e9090acc32348cedc5def0cd6d5c126efc97b9, 83e42a78428fc354f5e2049935b84c8d8d29b787 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
In the Linux kernel, the following vulnerability has been resolved: ubifs: Fix deadlock in concurrent rename whiteout and inode writeback Following hung tasks: [ 77.028764] task:kworker/u8:4 state:D stack: 0 pid: 132 [ 77.028820] Call Trace: [ 77.029027] schedule+0x8c/0x1b0 [ 77.029067] mutex_lock+0x50/0x60 [ 77.029074] ubifs_write_inode+0x68/0x1f0 [ubifs] [ 77.029117] __writeback_single_inode+0x43c/0x570 [ 77.029128] writeback_sb_inodes+0x259/0x740 [ 77.029148] wb_writeback+0x107/0x4d0 [ 77.029163] wb_workfn+0x162/0x7b0 [ 92.390442] task:aa state:D stack: 0 pid: 1506 [ 92.390448] Call Trace: [ 92.390458] schedule+0x8c/0x1b0 [ 92.390461] wb_wait_for_completion+0x82/0xd0 [ 92.390469] __writeback_inodes_sb_nr+0xb2/0x110 [ 92.390472] writeback_inodes_sb_nr+0x14/0x20 [ 92.390476] ubifs_budget_space+0x705/0xdd0 [ubifs] [ 92.390503] do_rename.cold+0x7f/0x187 [ubifs] [ 92.390549] ubifs_rename+0x8b/0x180 [ubifs] [ 92.390571] vfs_rename+0xdb2/0x1170 [ 92.390580] do_renameat2+0x554/0x770 , are caused by concurrent rename whiteout and inode writeback processes: rename_whiteout(Thread 1) wb_workfn(Thread2) ubifs_rename do_rename lock_4_inodes (Hold ui_mutex) ubifs_budget_space make_free_space shrink_liability __writeback_inodes_sb_nr bdi_split_work_to_wbs (Queue new wb work) wb_do_writeback(wb work) __writeback_single_inode ubifs_write_inode LOCK(ui_mutex) ↑ wb_wait_for_completion (Wait wb work) <-- deadlock! Reproducer (Detail program in [Link]): 1. SYS_renameat2("/mp/dir/file", "/mp/dir/whiteout", RENAME_WHITEOUT) 2. Consume out of space before kernel(mdelay) doing budget for whiteout Fix it by doing whiteout space budget before locking ubifs inodes. BTW, it also fixes wrong goto tag 'out_release' in whiteout budget error handling path(It should at least recover dir i_size and unlock 4 ubifs inodes).
- Published
- Feb 26, 2025
- Updated
- Jun 17, 2026
- EPSS
- 0.1% · 8th percentile
- CWE
- CWE-667
Report tools
Action score
22
Monitor
Low priority for now.
- CVSS
- 22 / 40 · 5.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.1%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| linux | linux kernel | cpe:2.3:o:linux:linux_kernel |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- linux linux kernel4.9 and later · before 4.19.238
- linux linux kernel4.20 and later · before 5.4.189
- linux linux kernel5.5 and later · before 5.10.110
- linux linux kernel5.11 and later · before 5.15.33
- linux linux kernel5.16 and later · before 5.16.19
- linux linux kernel5.17 and later · before 5.17.2
Versions reported by the vendor
Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.
Linux Linux
- 4.9affected
- 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and later · before 9dddc8211430fb851ddf0b168e3a00c6f66cc185affected · git
- 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and later · before 37bdf1ad592555ecda1d55b89f6e393e4c0589d1affected · git
- 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and later · before 83e42a78428fc354f5e2049935b84c8d8d29b787affected · git
- 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and later · before c58af8564a7b08757173009030b74baf4b2b762baffected · git
- 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and later · before 70e9090acc32348cedc5def0cd6d5c126efc97b9affected · git
- 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and later · before 8b278c8dcfb565cb65eceb62a38cbf7a7c326db5affected · git
- 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and later · before afd427048047e8efdedab30e8888044e2be5aa9caffected · git
- before 4.9not affected · semver
- 4.19.238 and later · up to and including 4.19.*not affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | linux | before 5.17.3-1 | 5.17.3-1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | kernel-64kb | before 5.14.21-150400.24.158.1 | 5.14.21-150400.24.158.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | kernel-docs | before 5.14.21-150400.24.158.1 | 5.14.21-150400.24.158.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | kernel-obs-build | before 5.14.21-150400.24.158.1 | 5.14.21-150400.24.158.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | kernel-source | before 5.14.21-150400.24.158.1 | 5.14.21-150400.24.158.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | kernel-syms | before 5.14.21-150400.24.158.1 | 5.14.21-150400.24.158.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | kernel-64kb | before 5.14.21-150500.55.100.1 | 5.14.21-150500.55.100.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | kernel-docs | before 5.14.21-150500.55.100.1 | 5.14.21-150500.55.100.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | kernel-obs-build | before 5.14.21-150500.55.100.1 | 5.14.21-150500.55.100.1 |
| SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | kernel-syms | before 5.14.21-150500.55.100.1 | 5.14.21-150500.55.100.1 |
| SUSE:Linux Enterprise Live Patching 15 SP4 | kernel-livepatch-SLE15-SP4_Update_38 | before 1-150400.9.3.1 | 1-150400.9.3.1 |
| SUSE:Linux Enterprise Live Patching 15 SP5 | kernel-livepatch-SLE15-SP5_Update_25 | before 1-150500.11.3.1 | 1-150500.11.3.1 |
| SUSE:Linux Enterprise Micro 5.3 | kernel-default | before 5.14.21-150400.24.158.1 | 5.14.21-150400.24.158.1 |
| SUSE:Linux Enterprise Micro 5.3 | kernel-default-base | before 5.14.21-150400.24.158.1.150400.24.78.1 | 5.14.21-150400.24.158.1.150400.24.78.1 |
| SUSE:Linux Enterprise Micro 5.3 | kernel-rt | before 5.14.21-150400.15.115.1 | 5.14.21-150400.15.115.1 |
| SUSE:Linux Enterprise Micro 5.3 | kernel-source-rt | before 5.14.21-150400.15.115.1 | 5.14.21-150400.15.115.1 |
| SUSE:Linux Enterprise Micro 5.5 | kernel-default | before 5.14.21-150500.55.100.1 | 5.14.21-150500.55.100.1 |
| SUSE:Linux Enterprise Micro 5.5 | kernel-default-base | before 5.14.21-150500.55.100.1.150500.6.47.1 | 5.14.21-150500.55.100.1.150500.6.47.1 |
| SUSE:Linux Enterprise Micro 5.5 | kernel-rt | before 5.14.21-150500.13.91.1 | 5.14.21-150500.13.91.1 |
| SUSE:Linux Enterprise Micro 5.5 | kernel-source | before 5.14.21-150500.55.100.1 | 5.14.21-150500.55.100.1 |
| SUSE:Linux Enterprise Micro 5.5 | kernel-source-rt | before 5.14.21-150500.13.91.1 | 5.14.21-150500.13.91.1 |
| SUSE:Linux Enterprise Server 15 SP4-LTSS | kernel-zfcpdump | before 5.14.21-150400.24.158.1 | 5.14.21-150400.24.158.1 |
| SUSE:Linux Enterprise Server 15 SP5-LTSS | kernel-zfcpdump | before 5.14.21-150500.55.100.1 | 5.14.21-150500.55.100.1 |
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV90Now
- CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV89Now
- CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV85Now
Published before and after this one in the same product
- ← EarlierCVE-2021-47635Feb 26, 2025 · ubifs: Fix to add refcount once page is set private22Monitor
- ← EarlierCVE-2021-47636Feb 26, 2025 · ubifs: Fix read out-of-bounds in ubifs_wbuf_write_nolock()28Monitor
- Later →CVE-2021-47638Feb 26, 2025 · ubifs: rename_whiteout: Fix double free for whiteout_ui->data22Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Linux Linux | 37bdf1ad592555ecda1d55b89f6e393e4c0589d1 | Vendor (CNA) |
| Linux Linux | 70e9090acc32348cedc5def0cd6d5c126efc97b9 | Vendor (CNA) |
| Linux Linux | 83e42a78428fc354f5e2049935b84c8d8d29b787 | Vendor (CNA) |
| Linux Linux | 8b278c8dcfb565cb65eceb62a38cbf7a7c326db5 | Vendor (CNA) |
| Linux Linux | 9dddc8211430fb851ddf0b168e3a00c6f66cc185 | Vendor (CNA) |
| Linux Linux | afd427048047e8efdedab30e8888044e2be5aa9c | Vendor (CNA) |
| Linux Linux | c58af8564a7b08757173009030b74baf4b2b762b | Vendor (CNA) |
| debian:linux | 5.17.3-1 · Debian:12 | Package registry (OSV) |
| suse:kernel-64kb | 5.14.21-150400.24.158.1 · SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | Package registry (OSV) |
| suse:kernel-default | 5.14.21-150400.24.158.1 · SUSE:Linux Enterprise Micro 5.3 | Package registry (OSV) |
| suse:kernel-default-base | 5.14.21-150400.24.158.1.150400.24.78.1 · SUSE:Linux Enterprise Micro 5.3 | Package registry (OSV) |
| suse:kernel-docs | 5.14.21-150400.24.158.1 · SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | Package registry (OSV) |
| suse:kernel-livepatch-SLE15-SP4_Update_38 | 1-150400.9.3.1 · SUSE:Linux Enterprise Live Patching 15 SP4 | Package registry (OSV) |
| suse:kernel-livepatch-SLE15-SP5_Update_25 | 1-150500.11.3.1 · SUSE:Linux Enterprise Live Patching 15 SP5 | Package registry (OSV) |
| suse:kernel-obs-build | 5.14.21-150400.24.158.1 · SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | Package registry (OSV) |
| suse:kernel-rt | 5.14.21-150500.13.91.1 · SUSE:Linux Enterprise Micro 5.5 | Package registry (OSV) |
| suse:kernel-source | 5.14.21-150400.24.158.1 · SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | Package registry (OSV) |
| suse:kernel-source-rt | 5.14.21-150500.13.91.1 · SUSE:Linux Enterprise Micro 5.5 | Package registry (OSV) |
| suse:kernel-syms | 5.14.21-150400.24.158.1 · SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | Package registry (OSV) |
| suse:kernel-zfcpdump | 5.14.21-150400.24.158.1 · SUSE:Linux Enterprise Server 15 SP4-LTSS | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
No history yet (it accumulates with the daily EPSS job).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Someone with local access to the system can trigger it.
- A low-privileged account is enough.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- high · the service can be disrupted
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
CWE-667 · Improper LockingCVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (6 more)Show less
- git.kernel.org/stable/c/70e9090acc32348cedc5def0cd6d5c126efc97b9
- git.kernel.org/stable/c/83e42a78428fc354f5e2049935b84c8d8d29b787
- git.kernel.org/stable/c/8b278c8dcfb565cb65eceb62a38cbf7a7c326db5
- git.kernel.org/stable/c/9dddc8211430fb851ddf0b168e3a00c6f66cc185
- git.kernel.org/stable/c/afd427048047e8efdedab30e8888044e2be5aa9c
- git.kernel.org/stable/c/c58af8564a7b08757173009030b74baf4b2b762b
Vendor advisories and official records. Exploit/PoC links are deliberately left out.