CVE-2021-47418: net_sched: fix NULL deref in fifo_set_limit()
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: 0.23% (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 08d7056e8e250fd2e67dbea5be5fdecdd75bf6b4, 0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52, 26af64d71b6277841285fa40e3f7164a378dfda9.
- Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).
Low priority for now. Upgrade to Linux Linux 08d7056e8e250fd2e67dbea5be5fdecdd75bf6b4, 0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52, 26af64d71b6277841285fa40e3f7164a378dfda9 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: net_sched: fix NULL deref in fifo_set_limit() syzbot reported another NULL deref in fifo_set_limit() [1] I could repro the issue with : unshare -n tc qd add dev lo root handle 1:0 tbf limit 200000 burst 70000 rate 100Mbit tc qd replace dev lo parent 1:0 pfifo_fast tc qd change dev lo root handle 1:0 tbf limit 300000 burst 70000 rate 100Mbit pfifo_fast does not have a change() operation. Make fifo_set_limit() more robust about this. [1] BUG: kernel NULL pointer dereference, address: 0000000000000000 PGD 1cf99067 P4D 1cf99067 PUD 7ca49067 PMD 0 Oops: 0010 [#1] PREEMPT SMP KASAN CPU: 1 PID: 14443 Comm: syz-executor959 Not tainted 5.15.0-rc3-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:0x0 Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6. RSP: 0018:ffffc9000e2f7310 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: ffffffff8d6ecc00 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff888024c27910 RDI: ffff888071e34000 RBP: ffff888071e34000 R08: 0000000000000001 R09: ffffffff8fcfb947 R10: 0000000000000001 R11: 0000000000000000 R12: ffff888024c27910 R13: ffff888071e34018 R14: 0000000000000000 R15: ffff88801ef74800 FS: 00007f321d897700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffffffffd6 CR3: 00000000722c3000 CR4: 00000000003506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: fifo_set_limit net/sched/sch_fifo.c:242 [inline] fifo_set_limit+0x198/0x210 net/sched/sch_fifo.c:227 tbf_change+0x6ec/0x16d0 net/sched/sch_tbf.c:418 qdisc_change net/sched/sch_api.c:1332 [inline] tc_modify_qdisc+0xd9a/0x1a60 net/sched/sch_api.c:1634 rtnetlink_rcv_msg+0x413/0xb80 net/core/rtnetlink.c:5572 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline] netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340 netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929 sock_sendmsg_nosec net/socket.c:704 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:724 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2409 ___sys_sendmsg+0xf3/0x170 net/socket.c:2463 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2492 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae
- Published
- May 21, 2024
- Updated
- Jun 17, 2026
- EPSS
- 0.2% · 14th percentile
- CWE
- CWE-476
Report tools
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.
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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.
We use this product, ask for helpAffected 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.
| Vendor | Product | CPE |
|---|---|---|
| linux | linux kernel | cpe:2.3:o:linux:linux_kernel |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- linux linux kernel2.6.27 and later · before 4.4.289
- linux linux kernel4.5 and later · before 4.9.287
- linux linux kernel4.10 and later · before 4.14.251
- linux linux kernel4.15 and later · before 4.19.211
- linux linux kernel4.20 and later · before 5.4.153
- linux linux kernel5.5 and later · before 5.10.73
- linux linux kernel5.11 and later · before 5.14.12
- 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
- 2.6.27affected
- fb0305ce1b03f6ff17f84f2c63daccecb45f2805 and later · before 0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52affected · git
- fb0305ce1b03f6ff17f84f2c63daccecb45f2805 and later · before 08d7056e8e250fd2e67dbea5be5fdecdd75bf6b4affected · git
- fb0305ce1b03f6ff17f84f2c63daccecb45f2805 and later · before 26af64d71b6277841285fa40e3f7164a378dfda9affected · git
- fb0305ce1b03f6ff17f84f2c63daccecb45f2805 and later · before d07098f45be868a9cdce6c616563c36c64dbbd87affected · git
- fb0305ce1b03f6ff17f84f2c63daccecb45f2805 and later · before c951a3be5e8803e93bb49a0aca0d30457d3c1b67affected · git
- fb0305ce1b03f6ff17f84f2c63daccecb45f2805 and later · before acff2d182c0768a713cee77442caeb07668bd68faffected · git
- fb0305ce1b03f6ff17f84f2c63daccecb45f2805 and later · before fb58cd7991747b5e0b110c98c922d7b0e47a1f14affected · git
- fb0305ce1b03f6ff17f84f2c63daccecb45f2805 and later · before 560ee196fe9e5037e5015e2cdb14b3aecb1cd7dcaffected · git
- before 2.6.27not affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | linux | before 5.14.12-1 | 5.14.12-1 |
| SUSE:Linux Enterprise Real Time 12 SP5 | kernel-rt | before 4.12.14-10.191.1 | 4.12.14-10.191.1 |
| SUSE:Linux Enterprise Real Time 12 SP5 | kernel-rt_debug | before 4.12.14-10.191.1 | 4.12.14-10.191.1 |
| SUSE:Linux Enterprise Real Time 12 SP5 | kernel-source-rt | before 4.12.14-10.191.1 | 4.12.14-10.191.1 |
| SUSE:Linux Enterprise Real Time 12 SP5 | kernel-syms-rt | before 4.12.14-10.191.1 | 4.12.14-10.191.1 |
| SUSE:Linux Enterprise Server 12 SP5 | kernel-azure | before 4.12.14-16.191.1 | 4.12.14-16.191.1 |
| SUSE:Linux Enterprise Server 12 SP5 | kernel-source-azure | before 4.12.14-16.191.1 | 4.12.14-16.191.1 |
| SUSE:Linux Enterprise Server 12 SP5 | kernel-syms-azure | before 4.12.14-16.191.1 | 4.12.14-16.191.1 |
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV90Now
- 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 KEV89Now
- CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV85Now
Published before and after this one in the same product
- ← EarlierCVE-2021-47416May 21, 2024 · phy: mdio: fix memory leak22Monitor
- ← EarlierCVE-2021-47417May 21, 2024 · libbpf: Fix memory leak in strset22Monitor
- Later →CVE-2021-47419May 21, 2024 · net/sched: sch_taprio: properly cancel timer from taprio_destroy()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 / package | Fixed version | Source |
|---|---|---|
| Linux Linux | 08d7056e8e250fd2e67dbea5be5fdecdd75bf6b4 | Vendor (CNA) |
| Linux Linux | 0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52 | Vendor (CNA) |
| Linux Linux | 26af64d71b6277841285fa40e3f7164a378dfda9 | Vendor (CNA) |
| Linux Linux | 560ee196fe9e5037e5015e2cdb14b3aecb1cd7dc | Vendor (CNA) |
| Linux Linux | acff2d182c0768a713cee77442caeb07668bd68f | Vendor (CNA) |
| Linux Linux | c951a3be5e8803e93bb49a0aca0d30457d3c1b67 | Vendor (CNA) |
| Linux Linux | d07098f45be868a9cdce6c616563c36c64dbbd87 | Vendor (CNA) |
| Linux Linux | fb58cd7991747b5e0b110c98c922d7b0e47a1f14 | Vendor (CNA) |
| debian:linux | 5.14.12-1 · Debian:12 | Package registry (OSV) |
| suse:kernel-azure | 4.12.14-16.191.1 · SUSE:Linux Enterprise Server 12 SP5 | Package registry (OSV) |
| suse:kernel-rt | 4.12.14-10.191.1 · SUSE:Linux Enterprise Real Time 12 SP5 | Package registry (OSV) |
| suse:kernel-rt_debug | 4.12.14-10.191.1 · SUSE:Linux Enterprise Real Time 12 SP5 | Package registry (OSV) |
| suse:kernel-source-azure | 4.12.14-16.191.1 · SUSE:Linux Enterprise Server 12 SP5 | Package registry (OSV) |
| suse:kernel-source-rt | 4.12.14-10.191.1 · SUSE:Linux Enterprise Real Time 12 SP5 | Package registry (OSV) |
| suse:kernel-syms-azure | 4.12.14-16.191.1 · SUSE:Linux Enterprise Server 12 SP5 | Package registry (OSV) |
| suse:kernel-syms-rt | 4.12.14-10.191.1 · SUSE:Linux Enterprise Real Time 12 SP5 | Package 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 researchersFinders, 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.
- TR-24-0519 · May 22, 2024(Linux Kernel Güncellemesi)
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 DereferenceCVSS 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
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (7 more)Show less
- git.kernel.org/stable/c/0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52
- git.kernel.org/stable/c/26af64d71b6277841285fa40e3f7164a378dfda9
- git.kernel.org/stable/c/560ee196fe9e5037e5015e2cdb14b3aecb1cd7dc
- git.kernel.org/stable/c/acff2d182c0768a713cee77442caeb07668bd68f
- git.kernel.org/stable/c/c951a3be5e8803e93bb49a0aca0d30457d3c1b67
- git.kernel.org/stable/c/d07098f45be868a9cdce6c616563c36c64dbbd87
- git.kernel.org/stable/c/fb58cd7991747b5e0b110c98c922d7b0e47a1f14
Vendor advisories and official records. Exploit/PoC links are deliberately left out.