Skip to content
Noroxi
NVD / CVE Program· CNA Linux

CVE-2021-47544: tcp: fix page frag corruption on page fault

Noroxi assessment

Priority: Monitor (action score 23/100)

  • 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: 0.86% (FIRST EPSS); higher than 58.5% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: Linux Linux 5a9afcd827cafe14a95c9fcbded2c2d104f18dfc, c6f340a331fb72e5ac23a083de9c780e132ca3ae, dacb5d8875cc6cd3a553363b4d6f06760fcbe70c.
  • Severity is disputed: the assigning authority (CNA) scores it 9.8, NVD 5.9.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 5a9afcd827cafe14a95c9fcbded2c2d104f18dfc, c6f340a331fb72e5ac23a083de9c780e132ca3ae, dacb5d8875cc6cd3a553363b4d6f06760fcbe70c 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: tcp: fix page frag corruption on page fault Steffen reported a TCP stream corruption for HTTP requests served by the apache web-server using a cifs mount-point and memory mapping the relevant file. The root cause is quite similar to the one addressed by commit 20eb4f29b602 ("net: fix sk_page_frag() recursion from memory reclaim"). Here the nested access to the task page frag is caused by a page fault on the (mmapped) user-space memory buffer coming from the cifs file. The page fault handler performs an smb transaction on a different socket, inside the same process context. Since sk->sk_allaction for such socket does not prevent the usage for the task_frag, the nested allocation modify "under the hood" the page frag in use by the outer sendmsg call, corrupting the stream. The overall relevant stack trace looks like the following: httpd 78268 [001] 3461630.850950: probe:tcp_sendmsg_locked: ffffffff91461d91 tcp_sendmsg_locked+0x1 ffffffff91462b57 tcp_sendmsg+0x27 ffffffff9139814e sock_sendmsg+0x3e ffffffffc06dfe1d smb_send_kvec+0x28 [...] ffffffffc06cfaf8 cifs_readpages+0x213 ffffffff90e83c4b read_pages+0x6b ffffffff90e83f31 __do_page_cache_readahead+0x1c1 ffffffff90e79e98 filemap_fault+0x788 ffffffff90eb0458 __do_fault+0x38 ffffffff90eb5280 do_fault+0x1a0 ffffffff90eb7c84 __handle_mm_fault+0x4d4 ffffffff90eb8093 handle_mm_fault+0xc3 ffffffff90c74f6d __do_page_fault+0x1ed ffffffff90c75277 do_page_fault+0x37 ffffffff9160111e page_fault+0x1e ffffffff9109e7b5 copyin+0x25 ffffffff9109eb40 _copy_from_iter_full+0xe0 ffffffff91462370 tcp_sendmsg_locked+0x5e0 ffffffff91462370 tcp_sendmsg_locked+0x5e0 ffffffff91462b57 tcp_sendmsg+0x27 ffffffff9139815c sock_sendmsg+0x4c ffffffff913981f7 sock_write_iter+0x97 ffffffff90f2cc56 do_iter_readv_writev+0x156 ffffffff90f2dff0 do_iter_write+0x80 ffffffff90f2e1c3 vfs_writev+0xa3 ffffffff90f2e27c do_writev+0x5c ffffffff90c042bb do_syscall_64+0x5b ffffffff916000ad entry_SYSCALL_64_after_hwframe+0x65 The cifs filesystem rightfully sets sk_allocations to GFP_NOFS, we can avoid the nesting using the sk page frag for allocation lacking the __GFP_FS flag. Do not define an additional mm-helper for that, as this is strictly tied to the sk page frag usage. v1 -> v2: - use a stricted sk_page_frag() check instead of reordering the code (Eric)

MediumCVSS 5.9 · v3.1—No exploit Fix available
Published
May 24, 2024
Updated
Aug 5, 2026
EPSS
0.8% · 58th percentile
CWE
—

Report tools

JSON

Action score

23

Monitor

Low priority for now.

CVSS
23 / 40 · 5.9 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.8%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.9
CNA · Linux
9.8
3.9 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.

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-2021-47544

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 kernel3.7 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

    • 3.7affected
    • 5640f7685831e088fe6c2e1f863a6805962f8e81 and later · before c6f340a331fb72e5ac23a083de9c780e132ca3aeaffected · git
    • 5640f7685831e088fe6c2e1f863a6805962f8e81 and later · before 5a9afcd827cafe14a95c9fcbded2c2d104f18dfcaffected · git
    • 5640f7685831e088fe6c2e1f863a6805962f8e81 and later · before dacb5d8875cc6cd3a553363b4d6f06760fcbe70caffected · git
    • before 3.7not affected · semver
    • 5.10.84 and later · up to and including 5.10.*not affected · semver
    • 5.15.7 and later · up to and including 5.15.*not affected · semver
    • 5.16 and laternot affected · original_commit_for_fix

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
Red Hat:rhel_aus:8.2::baseosbpftoolbefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseosbpftool-debuginfobefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernelbefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-abi-whitelistsbefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-corebefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-debugbefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-debug-corebefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-debug-debuginfobefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-debug-develbefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-debug-modulesbefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-debug-modules-extrabefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-debuginfobefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-debuginfo-common-x86_64before 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-develbefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-docbefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-modulesbefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-modules-extrabefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-toolsbefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-tools-debuginfobefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseoskernel-tools-libsbefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseosperfbefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseosperf-debuginfobefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2
Red Hat:rhel_aus:8.2::baseospython3-perfbefore 0:4.18.0-193.98.1.el8_20:4.18.0-193.98.1.el8_2

+40

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-2021-47541May 24, 2024 · net/mlx4_en: Fix an use-after-free bug in mlx4_en_try_alloc_resources()
    31Monitor
  • ← EarlierCVE-2021-47542May 24, 2024 · net: qlogic: qlcnic: Fix a NULL pointer dereference in qlcnic_83xx_add_rings()
    22Monitor
  • Later →CVE-2021-47546May 24, 2024 · ipv6: fix memory leak in fib6_rule_suppress
    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 Linux5a9afcd827cafe14a95c9fcbded2c2d104f18dfcVendor (CNA)
Linux Linuxc6f340a331fb72e5ac23a083de9c780e132ca3aeVendor (CNA)
Linux Linuxdacb5d8875cc6cd3a553363b4d6f06760fcbe70cVendor (CNA)
debian:linux5.15.15-1 · Debian:12Package registry (OSV)
red hat:bpftool0:4.18.0-305.40.1.el8_4 · Red Hat:rhel_eus:8.4::baseosPackage registry (OSV)
red hat:bpftool-debuginfo0:4.18.0-305.40.1.el8_4 · Red Hat:rhel_eus:8.4::baseosPackage registry (OSV)
red hat:kernel0:4.18.0-305.40.1.el8_4 · Red Hat:rhel_eus:8.4::baseosPackage registry (OSV)
red hat:kernel-abi-stablelists0:4.18.0-305.40.1.el8_4 · Red Hat:rhel_eus:8.4::baseosPackage registry (OSV)
red hat:kernel-core0:4.18.0-305.40.1.el8_4 · Red Hat:rhel_eus:8.4::baseosPackage registry (OSV)
red hat:kernel-debug0:4.18.0-305.40.1.el8_4 · Red Hat:rhel_eus:8.4::baseosPackage registry (OSV)
red hat:kernel-debug-core0:4.18.0-305.40.1.el8_4 · Red Hat:rhel_eus:8.4::baseosPackage registry (OSV)
red hat:kernel-debug-debuginfo0:4.18.0-305.40.1.el8_4 · Red Hat:rhel_eus:8.4::baseosPackage registry (OSV)
red hat:kernel-debug-devel0:4.18.0-305.40.1.el8_4 · Red Hat:rhel_eus:8.4::baseosPackage registry (OSV)
red hat:kernel-debug-modules0:4.18.0-305.40.1.el8_4 · Red Hat:rhel_eus:8.4::baseosPackage registry (OSV)
red hat:kernel-debug-modules-extra0:4.18.0-305.40.1.el8_4 · Red Hat:rhel_eus:8.4::baseosPackage registry (OSV)
red hat:kernel-debuginfo0:4.18.0-305.40.1.el8_4 · Red Hat:rhel_eus:8.4::baseosPackage registry (OSV)
suse:kernel-rt4.12.14-10.191.1 · SUSE:Linux Enterprise Real Time 12 SP5Package registry (OSV)
suse:kernel-rt_debug4.12.14-10.191.1 · SUSE:Linux Enterprise Real Time 12 SP5Package registry (OSV)
suse:kernel-source-rt4.12.14-10.191.1 · SUSE:Linux Enterprise Real Time 12 SP5Package registry (OSV)
suse:kernel-syms-rt4.12.14-10.191.1 · SUSE:Linux Enterprise Real Time 12 SP5Package 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).

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

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
none
Availability
none
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
None
Availability impact
None

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/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.

Change log

  1. Fix✗ → ✓

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

References

Show all references (2 more)

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

All records