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CVE-2021-47397· NVD / CVE Program· CNA Linux

sctp: break out if skb_header_pointer returns NULL in sctp_rcv_ootb

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: 0.77% (FIRST EPSS); higher than 55.3% of all records.
  • 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 77bc7dcf0fcc1519341a91788d7a2914fcfddf6d, 8180611c238e11676612eb2a9828b1c7a3a4d77b, 8c630a7b4f9dec63f08bd881ab77984a724a5124.
  • Severity is disputed: the assigning authority (CNA) scores it 7.5, NVD 5.5.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 77bc7dcf0fcc1519341a91788d7a2914fcfddf6d, 8180611c238e11676612eb2a9828b1c7a3a4d77b, 8c630a7b4f9dec63f08bd881ab77984a724a5124 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: sctp: break out if skb_header_pointer returns NULL in sctp_rcv_ootb We should always check if skb_header_pointer's return is NULL before using it, otherwise it may cause null-ptr-deref, as syzbot reported: KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:sctp_rcv_ootb net/sctp/input.c:705 [inline] RIP: 0010:sctp_rcv+0x1d84/0x3220 net/sctp/input.c:196 Call Trace: <IRQ> sctp6_rcv+0x38/0x60 net/sctp/ipv6.c:1109 ip6_protocol_deliver_rcu+0x2e9/0x1ca0 net/ipv6/ip6_input.c:422 ip6_input_finish+0x62/0x170 net/ipv6/ip6_input.c:463 NF_HOOK include/linux/netfilter.h:307 [inline] NF_HOOK include/linux/netfilter.h:301 [inline] ip6_input+0x9c/0xd0 net/ipv6/ip6_input.c:472 dst_input include/net/dst.h:460 [inline] ip6_rcv_finish net/ipv6/ip6_input.c:76 [inline] NF_HOOK include/linux/netfilter.h:307 [inline] NF_HOOK include/linux/netfilter.h:301 [inline] ipv6_rcv+0x28c/0x3c0 net/ipv6/ip6_input.c:297

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
May 21, 2024
Updated
Aug 5, 2026
EPSS
0.7% · 55th 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 · 0.7%

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
7.5
2.0 point gap

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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-2021-47397

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

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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 kernel4.8 and later · before 4.14.249
  • linux linux kernel4.15 and later · before 4.19.209
  • linux linux kernel4.20 and later · before 5.4.151
  • linux linux kernel5.5 and later · before 5.10.71
  • linux linux kernel5.11 and later · before 5.14.10
  • linux linux kernel5.15

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

    • 4.8affected
    • 3acb50c18d8d6650f10919464ade4dcdaf41d62f and later · before 77bc7dcf0fcc1519341a91788d7a2914fcfddf6daffected · git
    • 3acb50c18d8d6650f10919464ade4dcdaf41d62f and later · before 8c630a7b4f9dec63f08bd881ab77984a724a5124affected · git
    • 3acb50c18d8d6650f10919464ade4dcdaf41d62f and later · before ec018021cf445abbe8e2f3e2a7f1dcc813cb8ea1affected · git
    • 3acb50c18d8d6650f10919464ade4dcdaf41d62f and later · before 9c6591ae8e63f93c895ad5e2703c36c548aac997affected · git
    • 3acb50c18d8d6650f10919464ade4dcdaf41d62f and later · before 8180611c238e11676612eb2a9828b1c7a3a4d77baffected · git
    • 3acb50c18d8d6650f10919464ade4dcdaf41d62f and later · before f7e745f8e94492a8ac0b0a26e25f2b19d342918faffected · git
    • before 4.8not affected · semver
    • 4.14.249 and later · up to and including 4.14.*not affected · semver
    • 4.19.209 and later · up to and including 4.19.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 5.14.12-15.14.12-1

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-2021-47395May 21, 2024 · mac80211: limit injected vht mcs/nss in ieee80211_parse_tx_radiotap
    22Monitor
  • ← EarlierCVE-2021-47396May 21, 2024 · mac80211-hwsim: fix late beacon hrtimer handling
    22Monitor
  • Later →CVE-2021-47398May 21, 2024 · RDMA/hfi1: Fix kernel pointer leak
    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 Linux77bc7dcf0fcc1519341a91788d7a2914fcfddf6dVendor (CNA)
Linux Linux8180611c238e11676612eb2a9828b1c7a3a4d77bVendor (CNA)
Linux Linux8c630a7b4f9dec63f08bd881ab77984a724a5124Vendor (CNA)
Linux Linux9c6591ae8e63f93c895ad5e2703c36c548aac997Vendor (CNA)
Linux Linuxec018021cf445abbe8e2f3e2a7f1dcc813cb8ea1Vendor (CNA)
Linux Linuxf7e745f8e94492a8ac0b0a26e25f2b19d342918fVendor (CNA)
debian:linux5.14.12-1 · 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+1% in 7 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.

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-476 · NULL Pointer Dereference

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