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NVD / CVE Program· CNA Linux

CVE-2021-46935: binder: fix async_free_space accounting for empty parcels

MediumCVSS 5.5 · v3.1—No exploit Fix available

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: 0.22% (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 103b16a8c51f96d5fe063022869ea906c256e5da, 17691bada6b2f1d5f1c0f6d28cd9d0727023b0ff, 1cb8444f3114f0bb2f6e3bcadcf09aa4a28425d4.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 103b16a8c51f96d5fe063022869ea906c256e5da, 17691bada6b2f1d5f1c0f6d28cd9d0727023b0ff, 1cb8444f3114f0bb2f6e3bcadcf09aa4a28425d4 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: binder: fix async_free_space accounting for empty parcels In 4.13, commit 74310e06be4d ("android: binder: Move buffer out of area shared with user space") fixed a kernel structure visibility issue. As part of that patch, sizeof(void *) was used as the buffer size for 0-length data payloads so the driver could detect abusive clients sending 0-length asynchronous transactions to a server by enforcing limits on async_free_size. Unfortunately, on the "free" side, the accounting of async_free_space did not add the sizeof(void *) back. The result was that up to 8-bytes of async_free_space were leaked on every async transaction of 8-bytes or less. These small transactions are uncommon, so this accounting issue has gone undetected for several years. The fix is to use "buffer_size" (the allocated buffer size) instead of "size" (the logical buffer size) when updating the async_free_space during the free operation. These are the same except for this corner case of asynchronous transactions with payloads < 8 bytes.

Published
Feb 27, 2024
Updated
Jun 17, 2026
EPSS
0.2% · 13th 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 · 0.2%

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.

Follow CVE-2021-46935

When you'll hear from us

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • 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

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

    • 4.14affected
    • 74310e06be4d74dcf67cd108366710dee5c576d5 and later · before 2d2df539d05205fd83c404d5f2dff48d36f9b495affected · git
    • 74310e06be4d74dcf67cd108366710dee5c576d5 and later · before 7c7064402609aeb6fb11be1b4ec10673ff17b593affected · git
    • 74310e06be4d74dcf67cd108366710dee5c576d5 and later · before 103b16a8c51f96d5fe063022869ea906c256e5daaffected · git
    • 74310e06be4d74dcf67cd108366710dee5c576d5 and later · before 1cb8444f3114f0bb2f6e3bcadcf09aa4a28425d4affected · git
    • 74310e06be4d74dcf67cd108366710dee5c576d5 and later · before 17691bada6b2f1d5f1c0f6d28cd9d0727023b0ffaffected · git
    • 74310e06be4d74dcf67cd108366710dee5c576d5 and later · before cfd0d84ba28c18b531648c9d4a35ecca89ad9901affected · git
    • before 4.14not affected · semver
    • 4.14.261 and later · up to and including 4.14.*not affected · semver
    • 4.19.224 and later · up to and including 4.19.*not affected · semver
Affected versions · NVD (5)

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

  • linux linux kernel4.14.0 and later · before 4.14.261
  • linux linux kernel4.15.0 and later · before 4.19.224
  • linux linux kernel4.20.0 and later · before 5.4.170
  • linux linux kernel5.5.0 and later · before 5.10.90
  • linux linux kernel5.11.0 and later · before 5.15.13

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 5.15.15-15.15.15-1

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-2021-46933Feb 27, 2024 · usb: gadget: f_fs: Clear ffs_eventfd in ffs_data_clear.
    22Monitor
  • ← EarlierCVE-2021-46934Feb 27, 2024 · i2c: validate user data in compat ioctl
    13Monitor
  • Later →CVE-2021-46936Feb 27, 2024 · net: fix use-after-free in tw_timer_handler
    31Monitor

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 Linux103b16a8c51f96d5fe063022869ea906c256e5daVendor (CNA)
Linux Linux17691bada6b2f1d5f1c0f6d28cd9d0727023b0ffVendor (CNA)
Linux Linux1cb8444f3114f0bb2f6e3bcadcf09aa4a28425d4Vendor (CNA)
Linux Linux2d2df539d05205fd83c404d5f2dff48d36f9b495Vendor (CNA)
Linux Linux7c7064402609aeb6fb11be1b4ec10673ff17b593Vendor (CNA)
Linux Linuxcfd0d84ba28c18b531648c9d4a35ecca89ad9901Vendor (CNA)
debian:linux5.15.15-1 · 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.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2025-22069414 days apartriscv: fgraph: Fix stack layout to match __arch_ftrace_regs argument of ftrace_return_to_handler
    31Monitor
  • CVE-2024-3603293 days apartBluetooth: qca: fix info leak when fetching fw build id
    28Monitor
  • CVE-2024-3603393 days apartBluetooth: qca: fix info leak when fetching board id
    28Monitor
  • CVE-2022-48757114 days apartnet: fix information leakage in /proc/net/ptype
    28Monitor
  • CVE-2024-39499136 days apartvmci: prevent speculation leaks by sanitizing event in event_deliver()
    28Monitor
  • CVE-2024-43881175 days apartwifi: ath12k: change DMA direction while mapping reinjected packets
    28Monitor

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · public bounty program.

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
none
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-668 · Exposure of Resource to Wrong Sphere

CVSS vector

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

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.

References

Show all references (5 more)

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

All records