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CVE-2022-50335· NVD / CVE Program· CNA Linux

9p: set req refcount to zero to avoid uninitialized usage

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: 0.38% (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 1cabce56626a61f4f02452cba61ad4332a4b73f8, 26273ade77f54716e30dfd40ac6e85ceb54ac0f9, 4.20.
  • Severity is disputed: the assigning authority (CNA) scores it 9.8, NVD 5.5.

Low priority for now. Upgrade to Linux Linux 1cabce56626a61f4f02452cba61ad4332a4b73f8, 26273ade77f54716e30dfd40ac6e85ceb54ac0f9, 4.20 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: 9p: set req refcount to zero to avoid uninitialized usage When a new request is allocated, the refcount will be zero if it is reused, but if the request is newly allocated from slab, it is not fully initialized before being added to idr. If the p9_read_work got a response before the refcount initiated. It will use a uninitialized req, which will result in a bad request data struct. Here is the logs from syzbot. Corrupted memory at 0xffff88807eade00b [ 0xff 0x07 0x00 0x00 0x00 0x00 0x00 0x00 . . . . . . . . ] (in kfence-#110): p9_fcall_fini net/9p/client.c:248 [inline] p9_req_put net/9p/client.c:396 [inline] p9_req_put+0x208/0x250 net/9p/client.c:390 p9_client_walk+0x247/0x540 net/9p/client.c:1165 clone_fid fs/9p/fid.h:21 [inline] v9fs_fid_xattr_set+0xe4/0x2b0 fs/9p/xattr.c:118 v9fs_xattr_set fs/9p/xattr.c:100 [inline] v9fs_xattr_handler_set+0x6f/0x120 fs/9p/xattr.c:159 __vfs_setxattr+0x119/0x180 fs/xattr.c:182 __vfs_setxattr_noperm+0x129/0x5f0 fs/xattr.c:216 __vfs_setxattr_locked+0x1d3/0x260 fs/xattr.c:277 vfs_setxattr+0x143/0x340 fs/xattr.c:309 setxattr+0x146/0x160 fs/xattr.c:617 path_setxattr+0x197/0x1c0 fs/xattr.c:636 __do_sys_setxattr fs/xattr.c:652 [inline] __se_sys_setxattr fs/xattr.c:648 [inline] __ia32_sys_setxattr+0xc0/0x160 fs/xattr.c:648 do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline] __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178 do_fast_syscall_32+0x33/0x70 arch/x86/entry/common.c:203 entry_SYSENTER_compat_after_hwframe+0x70/0x82 Below is a similar scenario, the scenario in the syzbot log looks more complicated than this one, but this patch can fix it. T21124 p9_read_work ======================== second trans ================================= p9_client_walk p9_client_rpc p9_client_prepare_req p9_tag_alloc req = kmem_cache_alloc(p9_req_cache, GFP_NOFS); tag = idr_alloc << preempted >> req->tc.tag = tag; /* req->[refcount/tag] == uninitialized */ m->rreq = p9_tag_lookup(m->client, m->rc.tag); /* increments uninitalized refcount */ refcount_set(&req->refcount, 2); /* cb drops one ref */ p9_client_cb(req) /* reader thread drops its ref: request is incorrectly freed */ p9_req_put(req) /* use after free and ref underflow */ p9_req_put(req) To fix it, we can initialize the refcount to zero before add to idr.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Sep 15, 2025
Updated
Aug 5, 2026
EPSS
0.3% · 30th 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 · 0.3%

CNA vs NVD score

NVD
5.5
CNA · Linux
9.8
4.3 point gap

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • 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 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 kernel4.19.57 and later · before 5.15.86
  • linux linux kernel5.16 and later · before 6.0.16
  • linux linux kernel6.1 and later · before 6.1.2

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

    • 3665a4d9dca1bd06bc34afb72e637fe01b2776ee, 4.20affected
    • 728356dedeff8ef999cb436c71333ef4ac51a81c and later · before 1cabce56626a61f4f02452cba61ad4332a4b73f8affected · git
    • 728356dedeff8ef999cb436c71333ef4ac51a81c and later · before 73c47b3123b351de2d3714a72a336c0f72f203afaffected · git
    • 728356dedeff8ef999cb436c71333ef4ac51a81c and later · before 967fc34f297e40fd2e068cf6b0c3eb4916228539affected · git
    • 728356dedeff8ef999cb436c71333ef4ac51a81c and later · before 26273ade77f54716e30dfd40ac6e85ceb54ac0f9affected · git
    • 4.19.57 and later · before 4.20affected · semver
    • before 4.20not affected · semver
    • 5.15.86 and later · up to and including 5.15.*not affected · semver
    • 6.0.16 and later · up to and including 6.0.*not affected · semver
    • 6.1.2 and later · up to and including 6.1.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.4-16.1.4-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • 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
  • CVE-2016-5195Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect haKEV
    83Now

Published before and after this one in the same product

  • ← EarlierCVE-2022-50333Sep 15, 2025 · fs: jfs: fix shift-out-of-bounds in dbDiscardAG
    28Monitor
  • ← EarlierCVE-2022-50334Sep 15, 2025 · hugetlbfs: fix null-ptr-deref in hugetlbfs_parse_param()
    22Monitor
  • Later →CVE-2022-50336Sep 15, 2025 · fs/ntfs3: Add null pointer check to attr_load_runs_vcn
    22Monitor

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 Linux1cabce56626a61f4f02452cba61ad4332a4b73f8Vendor (CNA)
Linux Linux26273ade77f54716e30dfd40ac6e85ceb54ac0f9Vendor (CNA)
Linux Linux4.20Vendor (CNA)
Linux Linux73c47b3123b351de2d3714a72a336c0f72f203afVendor (CNA)
Linux Linux967fc34f297e40fd2e068cf6b0c3eb4916228539Vendor (CNA)
debian:linux6.1.4-1 · 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.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

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.

  • CVE-2024-50302300 days apartHID: core: zero-initialize the report bufferKEV
    52Plan
  • CVE-2026-52989282 days apartnvmet-tcp: propagate nvmet_tcp_build_pdu_iovec() errors to its callers
    39Monitor
  • CVE-2026-53225283 days apartsctp: fix uninit-value in __sctp_rcv_asconf_lookup()
    36Monitor
  • CVE-2024-47685329 days apartnetfilter: nf_reject_ipv6: fix nf_reject_ip6_tcphdr_put()
    36Monitor
  • CVE-2026-53170283 days apartaccel/ethosu: reject DMA commands with uninitialized length
    35Monitor
  • CVE-2026-43139233 days apartxfrm6: fix uninitialized saddr in xfrm6_get_saddr()
    34Monitor

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-908 · Use of Uninitialized Resource

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.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

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

References

Show all references (3 more)

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

All records