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NVD / CVE Program· CNA Linux

CVE-2025-21792: ax25: Fix refcount leak caused by setting SO_BINDTODEVICE sockopt

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: 0.24% (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 4.15, 4.20, 470bda72fda0fcf54300466d70ce2de62f7835d2; azl3 kernel 6.6.78.1-3 on Azure Linux 3.0 6.6.79.1-1; azl3 kernel 6.6.79.1-1 on Azure Linux 3.0 6.6.79.1-1.
  • Severity is disputed: the assigning authority (CNA) scores it 7.8, NVD 5.5.

Low priority for now. Upgrade to Linux Linux 4.15, 4.20, 470bda72fda0fcf54300466d70ce2de62f7835d2; azl3 kernel 6.6.78.1-3 on Azure Linux 3.0 6.6.79.1-1; azl3 kernel 6.6.79.1-1 on Azure Linux 3.0 6.6.79.1-1 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: ax25: Fix refcount leak caused by setting SO_BINDTODEVICE sockopt If an AX25 device is bound to a socket by setting the SO_BINDTODEVICE socket option, a refcount leak will occur in ax25_release(). Commit 9fd75b66b8f6 ("ax25: Fix refcount leaks caused by ax25_cb_del()") added decrement of device refcounts in ax25_release(). In order for that to work correctly the refcounts must already be incremented when the device is bound to the socket. An AX25 device can be bound to a socket by either calling ax25_bind() or setting SO_BINDTODEVICE socket option. In both cases the refcounts should be incremented, but in fact it is done only in ax25_bind(). This bug leads to the following issue reported by Syzkaller: ================================================================ refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 1 PID: 5932 at lib/refcount.c:31 refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31 Modules linked in: CPU: 1 UID: 0 PID: 5932 Comm: syz-executor424 Not tainted 6.13.0-rc4-syzkaller-00110-g4099a71718b0 #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31 Call Trace: <TASK> __refcount_dec include/linux/refcount.h:336 [inline] refcount_dec include/linux/refcount.h:351 [inline] ref_tracker_free+0x710/0x820 lib/ref_tracker.c:236 netdev_tracker_free include/linux/netdevice.h:4156 [inline] netdev_put include/linux/netdevice.h:4173 [inline] netdev_put include/linux/netdevice.h:4169 [inline] ax25_release+0x33f/0xa10 net/ax25/af_ax25.c:1069 __sock_release+0xb0/0x270 net/socket.c:640 sock_close+0x1c/0x30 net/socket.c:1408 ... do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f ... </TASK> ================================================================ Fix the implementation of ax25_setsockopt() by adding increment of refcounts for the new device bound, and decrement of refcounts for the old unbound device.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Feb 26, 2025
Updated
Aug 5, 2026
EPSS
0.2% · 15th percentile
CWE
—

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 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.5
CNA · Linux
7.8
2.3 point gap

CVSS:3.1/AV:L/AC:L/PR:L/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.

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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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 kernel4.14.277 and later · before 4.15
  • linux linux kernel4.19.240 and later · before 4.20
  • linux linux kernel5.4.190 and later · before 5.5
  • linux linux kernel5.10.112 and later · before 5.11
  • linux linux kernel5.15.35 and later · before 5.16
  • linux linux kernel5.17.2 and later · before 6.1.129
  • linux linux kernel6.2 and later · before 6.6.79
  • linux linux kernel6.7 and later · before 6.12.16
  • linux linux kernel6.13 and later · before 6.13.4
  • linux linux kernel6.14

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

    • c44a453ffe16eb08acdc6129ac4fa0192dbc0456, de55a1338e6a48ff1e41ea8db1432496fbe2a62b, 9e1e088a57c23251f1cfe9601bbd90ade2ea73b9, b20a5ab0f5fb175750c6bafd4cf12daccf00c738, 452ae92b99062d2f6a34324eaf705a3b7eac9f8b, 534156dd4ed768e30a43de0036f45dca7c54818f, 5.18affected
    • 9fd75b66b8f68498454d685dc4ba13192ae069b0 and later · before 90056ece99966182dc0e367f3fd2afab46ada847affected · git
    • 9fd75b66b8f68498454d685dc4ba13192ae069b0 and later · before 94a0de224ed52eb2ecd4f4cb1b937b674c9fb955affected · git
    • 9fd75b66b8f68498454d685dc4ba13192ae069b0 and later · before b58f7ca86a7b8e480c06e30c5163c5d2f4e24023affected · git
    • 9fd75b66b8f68498454d685dc4ba13192ae069b0 and later · before 470bda72fda0fcf54300466d70ce2de62f7835d2affected · git
    • 9fd75b66b8f68498454d685dc4ba13192ae069b0 and later · before bca0902e61731a75fc4860c8720168d9f1bae3b6affected · git
    • 4.14.277 and later · before 4.15affected · semver
    • 4.19.240 and later · before 4.20affected · semver
    • 5.4.190 and later · before 5.5affected · semver
    • 5.10.112 and later · before 5.11affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.129-16.1.129-1
Debian:13linuxbefore 6.12.16-16.12.16-1

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-2025-21788Feb 26, 2025 · net: ethernet: ti: am65-cpsw: fix memleak in certain XDP cases
    22Monitor
  • ← EarlierCVE-2025-21789Feb 26, 2025 · LoongArch: csum: Fix OoB access in IP checksum code for negative lengths
    28Monitor
  • Later →CVE-2025-21793Feb 26, 2025 · spi: sn-f-ospi: Fix division by zero
    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 Linux4.15Vendor (CNA)
Linux Linux4.20Vendor (CNA)
Linux Linux470bda72fda0fcf54300466d70ce2de62f7835d2Vendor (CNA)
Linux Linux5.11Vendor (CNA)
Linux Linux5.16Vendor (CNA)
Linux Linux5.18Vendor (CNA)
Linux Linux5.5Vendor (CNA)
Linux Linux90056ece99966182dc0e367f3fd2afab46ada847Vendor (CNA)
Linux Linux94a0de224ed52eb2ecd4f4cb1b937b674c9fb955Vendor (CNA)
Linux Linuxb58f7ca86a7b8e480c06e30c5163c5d2f4e24023Vendor (CNA)
Linux Linuxbca0902e61731a75fc4860c8720168d9f1bae3b6Vendor (CNA)
azl3 kernel 6.6.78.1-3 on Azure Linux 3.06.6.79.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
azl3 kernel 6.6.79.1-1 on Azure Linux 3.06.6.79.1-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
debian:linux6.1.129-1 · 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)

—

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 (5 more)

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

All records