Skip to content
Noroxi
NVD / CVE Program· CNA Linux

CVE-2021-47527: serial: core: fix transmit-buffer reset and memleak

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: 0.25% (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 00de977f9e0aa9760d9a79d1e41ff780f74e3424, 011f6c92b5bf6e1fbfdedc8b5232f64c1c493206, 1179b168fa3f3a6aae3bd140000455a0e58457db.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 00de977f9e0aa9760d9a79d1e41ff780f74e3424, 011f6c92b5bf6e1fbfdedc8b5232f64c1c493206, 1179b168fa3f3a6aae3bd140000455a0e58457db 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: serial: core: fix transmit-buffer reset and memleak Commit 761ed4a94582 ("tty: serial_core: convert uart_close to use tty_port_close") converted serial core to use tty_port_close() but failed to notice that the transmit buffer still needs to be freed on final close. Not freeing the transmit buffer means that the buffer is no longer cleared on next open so that any ioctl() waiting for the buffer to drain might wait indefinitely (e.g. on termios changes) or that stale data can end up being transmitted in case tx is restarted. Furthermore, the buffer of any port that has been opened would leak on driver unbind. Note that the port lock is held when clearing the buffer pointer due to the ldisc race worked around by commit a5ba1d95e46e ("uart: fix race between uart_put_char() and uart_shutdown()"). Also note that the tty-port shutdown() callback is not called for console ports so it is not strictly necessary to free the buffer page after releasing the lock (cf. d72402145ace ("tty/serial: do not free trasnmit buffer page under port lock")).

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
May 24, 2024
Updated
Jun 17, 2026
EPSS
0.2% · 16th 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-2021-47527

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for linux records

Running WordPress? Scan your site free with WP Lens

Is your version affected? Check it

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 help

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 kernel4.9 and later · before 4.9.292
  • linux linux kernel4.10 and later · before 4.14.257
  • linux linux kernel4.15 and later · before 4.19.220
  • linux linux kernel4.20 and later · before 5.4.164
  • linux linux kernel5.5 and later · before 5.10.84
  • linux linux kernel5.11 and later · before 5.15.7
  • linux linux kernel5.16

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

    • 4.9affected
    • 761ed4a94582ab291aa24dcbea4e01e8936488c8 and later · before 011f6c92b5bf6e1fbfdedc8b5232f64c1c493206affected · git
    • 761ed4a94582ab291aa24dcbea4e01e8936488c8 and later · before e74d9663fd57640fc3394abb5c76fa95b9cc2f2eaffected · git
    • 761ed4a94582ab291aa24dcbea4e01e8936488c8 and later · before 1179b168fa3f3a6aae3bd140000455a0e58457dbaffected · git
    • 761ed4a94582ab291aa24dcbea4e01e8936488c8 and later · before c5da8aa441053958594f94254592bb41264bdfbfaffected · git
    • 761ed4a94582ab291aa24dcbea4e01e8936488c8 and later · before e1722acf4f0d4d67b60f57e08ce16f8b66cd4b8faffected · git
    • 761ed4a94582ab291aa24dcbea4e01e8936488c8 and later · before 64e491c1634b73d3bddc081d08620bdc92ab2c12affected · git
    • 761ed4a94582ab291aa24dcbea4e01e8936488c8 and later · before 00de977f9e0aa9760d9a79d1e41ff780f74e3424affected · git
    • before 4.9not affected · semver
    • 4.9.292 and later · up to and including 4.9.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
AlmaLinux:8bpftoolbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernelbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-abi-stablelistsbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-corebefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-cross-headersbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debugbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debug-corebefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debug-develbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debug-modulesbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debug-modules-extrabefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-develbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-docbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-headersbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-modulesbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-modules-extrabefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-rtbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-corebefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debugbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-corebefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-develbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-kvmbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-modulesbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-modules-extrabefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-develbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10

+96

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-2021-47525May 24, 2024 · serial: liteuart: fix use-after-free and memleak on unbind
    31Monitor
  • ← EarlierCVE-2021-47526May 24, 2024 · serial: liteuart: Fix NULL pointer dereference in ->remove()
    22Monitor
  • Later →CVE-2021-47528May 24, 2024 · usb: cdnsp: Fix a NULL pointer dereference in cdnsp_endpoint_init()
    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 Linux00de977f9e0aa9760d9a79d1e41ff780f74e3424Vendor (CNA)
Linux Linux011f6c92b5bf6e1fbfdedc8b5232f64c1c493206Vendor (CNA)
Linux Linux1179b168fa3f3a6aae3bd140000455a0e58457dbVendor (CNA)
Linux Linux64e491c1634b73d3bddc081d08620bdc92ab2c12Vendor (CNA)
Linux Linuxc5da8aa441053958594f94254592bb41264bdfbfVendor (CNA)
Linux Linuxe1722acf4f0d4d67b60f57e08ce16f8b66cd4b8fVendor (CNA)
Linux Linuxe74d9663fd57640fc3394abb5c76fa95b9cc2f2eVendor (CNA)
almalinux:bpftool4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-abi-stablelists4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-core4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-cross-headers4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-core4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-devel4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules-extra4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-devel4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-doc4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
debian:linux5.15.15-1 · Debian:12Package registry (OSV)
red hat:bpftool0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:bpftool-debuginfo0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-abi-stablelists0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-core0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug-core0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug-debuginfo0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug-devel0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug-modules0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)

+4

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).

National notice (Türkiye Cybersecurity Directorate / USOM)

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

All national notices →

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-401 · Missing Release of Memory after Effective Lifetime

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 (6 more)

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

All records