CVE-2021-47636: ubifs: Fix read out-of-bounds in ubifs_wbuf_write_nolock()
Noroxi assessment
Priority: Monitor (action score 28/100)
- 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: 0.26% (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 07a209fadee7b53b46858538e1177597273862e4, 3b7fb89135a20587d57f8877c02e25003e9edbdf, 4f2262a334641e05f645364d5ade1f565c85f20b.
Low priority for now. Upgrade to Linux Linux 07a209fadee7b53b46858538e1177597273862e4, 3b7fb89135a20587d57f8877c02e25003e9edbdf, 4f2262a334641e05f645364d5ade1f565c85f20b 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 read out-of-bounds in ubifs_wbuf_write_nolock() Function ubifs_wbuf_write_nolock() may access buf out of bounds in following process: ubifs_wbuf_write_nolock(): aligned_len = ALIGN(len, 8); // Assume len = 4089, aligned_len = 4096 if (aligned_len <= wbuf->avail) ... // Not satisfy if (wbuf->used) { ubifs_leb_write() // Fill some data in avail wbuf len -= wbuf->avail; // len is still not 8-bytes aligned aligned_len -= wbuf->avail; } n = aligned_len >> c->max_write_shift; if (n) { n <<= c->max_write_shift; err = ubifs_leb_write(c, wbuf->lnum, buf + written, wbuf->offs, n); // n > len, read out of bounds less than 8(n-len) bytes } , which can be catched by KASAN: ========================================================= BUG: KASAN: slab-out-of-bounds in ecc_sw_hamming_calculate+0x1dc/0x7d0 Read of size 4 at addr ffff888105594ff8 by task kworker/u8:4/128 Workqueue: writeback wb_workfn (flush-ubifs_0_0) Call Trace: kasan_report.cold+0x81/0x165 nand_write_page_swecc+0xa9/0x160 ubifs_leb_write+0xf2/0x1b0 [ubifs] ubifs_wbuf_write_nolock+0x421/0x12c0 [ubifs] write_head+0xdc/0x1c0 [ubifs] ubifs_jnl_write_inode+0x627/0x960 [ubifs] wb_workfn+0x8af/0xb80 Function ubifs_wbuf_write_nolock() accepts that parameter 'len' is not 8 bytes aligned, the 'len' represents the true length of buf (which is allocated in 'ubifs_jnl_xxx', eg. ubifs_jnl_write_inode), so ubifs_wbuf_write_nolock() must handle the length read from 'buf' carefully to write leb safely. Fetch a reproducer in [Link].
- Published
- Feb 26, 2025
- Updated
- Aug 5, 2026
- EPSS
- 0.2% · 17th percentile
- CWE
- CWE-125
Report tools
Action score
28
Monitor
Low priority for now.
- CVSS
- 28 / 40 · 7.1 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 7.1
- CNA · Linux
- 7.1
- agree
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
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 kernel2.6.27 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
- 2.6.27affected
- 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d and later · before 5343575aa11c5d7044107d59d43f84aec01312b0affected · git
- 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d and later · before b80ccbec0e4804436c382d7dd60e943c386ed83aaffected · git
- 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d and later · before 07a209fadee7b53b46858538e1177597273862e4affected · git
- 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d and later · before a7054aaf1909cf40489c0ec1b728fdcf79c751a6affected · git
- 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d and later · before e09fa5318d51f522e1af4fbaf8f74999355980c8affected · git
- 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d and later · before 3b7fb89135a20587d57f8877c02e25003e9edbdfaffected · git
- 1e51764a3c2ac05a23a22b2a95ddee4d9bffb16d and later · before 4f2262a334641e05f645364d5ade1f565c85f20baffected · git
- before 2.6.27not 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-2021-47634Feb 26, 2025 · ubi: Fix race condition between ctrl_cdev_ioctl and ubi_cdev_ioctl31Monitor
- ← EarlierCVE-2021-47635Feb 26, 2025 · ubifs: Fix to add refcount once page is set private22Monitor
- Later →CVE-2021-47637Feb 26, 2025 · ubifs: Fix deadlock in concurrent rename whiteout and inode writeback22Monitor
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 | 07a209fadee7b53b46858538e1177597273862e4 | Vendor (CNA) |
| Linux Linux | 3b7fb89135a20587d57f8877c02e25003e9edbdf | Vendor (CNA) |
| Linux Linux | 4f2262a334641e05f645364d5ade1f565c85f20b | Vendor (CNA) |
| Linux Linux | 5343575aa11c5d7044107d59d43f84aec01312b0 | Vendor (CNA) |
| Linux Linux | a7054aaf1909cf40489c0ec1b728fdcf79c751a6 | Vendor (CNA) |
| Linux Linux | b80ccbec0e4804436c382d7dd60e943c386ed83a | Vendor (CNA) |
| Linux Linux | e09fa5318d51f522e1af4fbaf8f74999355980c8 | 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
- high · data can be read
- 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
- High
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
CWE-125 · Out-of-bounds ReadCVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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.
Attack patterns (CAPEC)
ATT&CK techniques
—
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/3b7fb89135a20587d57f8877c02e25003e9edbdf
- git.kernel.org/stable/c/4f2262a334641e05f645364d5ade1f565c85f20b
- git.kernel.org/stable/c/5343575aa11c5d7044107d59d43f84aec01312b0
- git.kernel.org/stable/c/a7054aaf1909cf40489c0ec1b728fdcf79c751a6
- git.kernel.org/stable/c/b80ccbec0e4804436c382d7dd60e943c386ed83a
- git.kernel.org/stable/c/e09fa5318d51f522e1af4fbaf8f74999355980c8
Vendor advisories and official records. Exploit/PoC links are deliberately left out.