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NVD / CVE Program· CNA Linux

CVE-2022-49850: nilfs2: fix deadlock in nilfs_count_free_blocks()

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: 0.16% (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 1d4ff73062096c21b47954d2996b4df259777bda, 36ff974b0310771417c0be64b64aa221bd70d63d, 3c89ca6d3dfa6c09c515807a7a97a521f5d5147e.

Low priority for now. Upgrade to Linux Linux 1d4ff73062096c21b47954d2996b4df259777bda, 36ff974b0310771417c0be64b64aa221bd70d63d, 3c89ca6d3dfa6c09c515807a7a97a521f5d5147e 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: nilfs2: fix deadlock in nilfs_count_free_blocks() A semaphore deadlock can occur if nilfs_get_block() detects metadata corruption while locating data blocks and a superblock writeback occurs at the same time: task 1 task 2 ------ ------ * A file operation * nilfs_truncate() nilfs_get_block() down_read(rwsem A) <-- nilfs_bmap_lookup_contig() ... generic_shutdown_super() nilfs_put_super() * Prepare to write superblock * down_write(rwsem B) <-- nilfs_cleanup_super() * Detect b-tree corruption * nilfs_set_log_cursor() nilfs_bmap_convert_error() nilfs_count_free_blocks() __nilfs_error() down_read(rwsem A) <-- nilfs_set_error() down_write(rwsem B) <-- *** DEADLOCK *** Here, nilfs_get_block() readlocks rwsem A (= NILFS_MDT(dat_inode)->mi_sem) and then calls nilfs_bmap_lookup_contig(), but if it fails due to metadata corruption, __nilfs_error() is called from nilfs_bmap_convert_error() inside the lock section. Since __nilfs_error() calls nilfs_set_error() unless the filesystem is read-only and nilfs_set_error() attempts to writelock rwsem B (= nilfs->ns_sem) to write back superblock exclusively, hierarchical lock acquisition occurs in the order rwsem A -> rwsem B. Now, if another task starts updating the superblock, it may writelock rwsem B during the lock sequence above, and can deadlock trying to readlock rwsem A in nilfs_count_free_blocks(). However, there is actually no need to take rwsem A in nilfs_count_free_blocks() because it, within the lock section, only reads a single integer data on a shared struct with nilfs_sufile_get_ncleansegs(). This has been the case after commit aa474a220180 ("nilfs2: add local variable to cache the number of clean segments"), that is, even before this bug was introduced. So, this resolves the deadlock problem by just not taking the semaphore in nilfs_count_free_blocks().

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
May 1, 2025
Updated
Jun 17, 2026
EPSS
0.1% · 5th percentile

Report tools

JSON

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

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When you'll hear from us

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  • when exploit code appears or is weaponized
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  • when EPSS rises 20 points in a week

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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.

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Affected 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.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel2.6.38 and later · before 4.9.334
  • linux linux kernel4.10 and later · before 4.14.300
  • linux linux kernel4.15 and later · before 4.19.267
  • linux linux kernel4.20 and later · before 5.4.225
  • linux linux kernel5.5 and later · before 5.10.155
  • linux linux kernel5.11 and later · before 5.15.79
  • linux linux kernel5.16 and later · before 6.0.9
  • linux linux kernel6.1

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

    • 2.6.38affected
    • e828949e5b42bfd234ee537cdb7c5e3a577958a3 and later · before 3c89ca6d3dfa6c09c515807a7a97a521f5d5147eaffected · git
    • e828949e5b42bfd234ee537cdb7c5e3a577958a3 and later · before 8b4506cff6630bb474bb46a2a75c31e533a756baaffected · git
    • e828949e5b42bfd234ee537cdb7c5e3a577958a3 and later · before f0cc93080d4c09510b74ecba87fd778cca390bb1affected · git
    • e828949e5b42bfd234ee537cdb7c5e3a577958a3 and later · before 36ff974b0310771417c0be64b64aa221bd70d63daffected · git
    • e828949e5b42bfd234ee537cdb7c5e3a577958a3 and later · before 1d4ff73062096c21b47954d2996b4df259777bdaaffected · git
    • e828949e5b42bfd234ee537cdb7c5e3a577958a3 and later · before abc082aac0d9b6b926038fc3adb7008306581be2affected · git
    • e828949e5b42bfd234ee537cdb7c5e3a577958a3 and later · before cb029b54953420f7a2d65100f1c5107f14411bdcaffected · git
    • e828949e5b42bfd234ee537cdb7c5e3a577958a3 and later · before 8ac932a4921a96ca52f61935dbba64ea87bbd5dcaffected · git
    • before 2.6.38not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.0.10-16.0.10-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • 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 KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2022-49848May 1, 2025 · phy: qcom-qmp-combo: fix NULL-deref on runtime resume
    22Monitor
  • ← EarlierCVE-2022-49849May 1, 2025 · btrfs: fix match incorrectly in dev_args_match_device
    22Monitor
  • Later →CVE-2022-49851May 1, 2025 · riscv: fix reserved memory setup
    28Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux1d4ff73062096c21b47954d2996b4df259777bdaVendor (CNA)
Linux Linux36ff974b0310771417c0be64b64aa221bd70d63dVendor (CNA)
Linux Linux3c89ca6d3dfa6c09c515807a7a97a521f5d5147eVendor (CNA)
Linux Linux8ac932a4921a96ca52f61935dbba64ea87bbd5dcVendor (CNA)
Linux Linux8b4506cff6630bb474bb46a2a75c31e533a756baVendor (CNA)
Linux Linuxabc082aac0d9b6b926038fc3adb7008306581be2Vendor (CNA)
Linux Linuxcb029b54953420f7a2d65100f1c5107f14411bdcVendor (CNA)
Linux Linuxf0cc93080d4c09510b74ecba87fd778cca390bb1Vendor (CNA)
debian:linux6.0.10-1 · Debian:12Package 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 researchers

Finders, 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 Locking

CVSS 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

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records