CVE-2021-47136

MEDIUMNVD 5.55.5—
EchelonGraph scoreMEDIUM confidence

Score 5.5 from GitHub Security Advisory published 2024-03-25. NVD baseline CVSS 5.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
5.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

In the Linux kernel, the following vulnerability has been resolved:

net: zero-initialize tc skb extension on allocation

Function skb_ext_add() doesn't initialize created skb extension with any value and leaves it up to the user. However, since extension of type TC_SKB_EXT originally contained only single value tc_skb_ext->chain its users used to just assign the chain value without setting whole extension memory to zero first. This assumption changed when TC_SKB_EXT extension was extended with additional fields but not all users were updated to initialize the new fields which leads to use of uninitialized memory afterwards. UBSAN log:

[ 778.299821] UBSAN: invalid-load in net/openvswitch/flow.c:899:28 [ 778.301495] load of value 107 is not a valid value for type '_Bool' [ 778.303215] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.12.0-rc7+ #2 [ 778.304933] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 [ 778.307901] Call Trace: [ 778.308680] [ 778.309358] dump_stack+0xbb/0x107 [ 778.310307] ubsan_epilogue+0x5/0x40 [ 778.311167] __ubsan_handle_load_invalid_value.cold+0x43/0x48 [ 778.312454] ? memset+0x20/0x40 [ 778.313230] ovs_flow_key_extract.cold+0xf/0x14 [openvswitch] [ 778.314532] ovs_vport_receive+0x19e/0x2e0 [openvswitch] [ 778.315749] ? ovs_vport_find_upcall_portid+0x330/0x330 [openvswitch] [ 778.317188] ? create_prof_cpu_mask+0x20/0x20 [ 778.318220] ? arch_stack_walk+0x82/0xf0 [ 778.319153] ? secondary_startup_64_no_verify+0xb0/0xbb [ 778.320399] ? stack_trace_save+0x91/0xc0 [ 778.321362] ? stack_trace_consume_entry+0x160/0x160 [ 778.322517] ? lock_release+0x52e/0x760 [ 778.323444] netdev_frame_hook+0x323/0x610 [openvswitch] [ 778.324668] ? ovs_netdev_get_vport+0xe0/0xe0 [openvswitch] [ 778.325950] __netif_receive_skb_core+0x771/0x2db0 [ 778.327067] ? lock_downgrade+0x6e0/0x6f0 [ 778.328021] ? lock_acquire+0x565/0x720 [ 778.328940] ? generic_xdp_tx+0x4f0/0x4f0 [ 778.329902] ? inet_gro_receive+0x2a7/0x10a0 [ 778.330914] ? lock_downgrade+0x6f0/0x6f0 [ 778.331867] ? udp4_gro_receive+0x4c4/0x13e0 [ 778.332876] ? lock_release+0x52e/0x760 [ 778.333808] ? dev_gro_receive+0xcc8/0x2380 [ 778.334810] ? lock_downgrade+0x6f0/0x6f0 [ 778.335769] __netif_receive_skb_list_core+0x295/0x820 [ 778.336955] ? process_backlog+0x780/0x780 [ 778.337941] ? mlx5e_rep_tc_netdevice_event_unregister+0x20/0x20 [mlx5_core] [ 778.339613] ? seqcount_lockdep_reader_access.constprop.0+0xa7/0xc0 [ 778.341033] ? kvm_clock_get_cycles+0x14/0x20 [ 778.342072] netif_receive_skb_list_internal+0x5f5/0xcb0 [ 778.343288] ? __kasan_kmalloc+0x7a/0x90 [ 778.344234] ? mlx5e_handle_rx_cqe_mpwrq+0x9e0/0x9e0 [mlx5_core] [ 778.345676] ? mlx5e_xmit_xdp_frame_mpwqe+0x14d0/0x14d0 [mlx5_core] [ 778.347140] ? __netif_receive_skb_list_core+0x820/0x820 [ 778.348351] ? mlx5e_post_rx_mpwqes+0xa6/0x25d0 [mlx5_core] [ 778.349688] ? napi_gro_flush+0x26c/0x3c0 [ 778.350641] napi_complete_done+0x188/0x6b0 [ 778.351627] mlx5e_napi_poll+0x373/0x1b80 [mlx5_core] [ 778.352853] __napi_poll+0x9f/0x510 [ 778.353704] ? mlx5_flow_namespace_set_mode+0x260/0x260 [mlx5_core] [ 778.355158] net_rx_action+0x34c/0xa40 [ 778.356060] ? napi_threaded_poll+0x3d0/0x3d0 [ 778.357083] ? sched_clock_cpu+0x18/0x190 [ 778.358041] ? __common_interrupt+0x8e/0x1a0 [ 778.359045] __do_softirq+0x1ce/0x984 [ 778.359938] __irq_exit_rcu+0x137/0x1d0 [ 778.360865] irq_exit_rcu+0xa/0x20 [ 778.361708] common_interrupt+0x80/0xa0 [ 778.362640] [ 778.363212] asm_common_interrupt+0x1e/0x40 [ 778.364204] RIP: 0010:native_safe_halt+0xe/0x10 [ 778.365273] Code: 4f ff ff ff 4c 89 e7 e8 50 3f 40 fe e9 dc fe ff ff 48 89 df e8 43 3f 40 fe eb 90 cc e9 07 00 00 00 0f 00 2d 74 05 62 00 fb f4 90 e9 07 00 00 00 0f 00 2d 64 05 62 00 f4 c3 cc cc 0f 1f 44 00 [ 778.369355] RSP: 0018:ffffffff84407e48 EFLAGS: 00000246 [ 778.370570] RAX ---truncated---

CVSS v3
5.5
EG Score
5.5(medium)
EG Risk
25(Track)
EG Risk 25/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity55% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
14.2%
KEV
Not listed

Published

March 25, 2024

Last Modified

March 13, 2025

References (6)

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 50× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 101 total refreshes for this CVE.

  1. 2026-07-23 02:06 UTCEG score recompute
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Frequently asked(5)

What is CVE-2021-47136?
CVE-2021-47136 is a medium vulnerability published on March 25, 2024. In the Linux kernel, the following vulnerability has been resolved: net: zero-initialize tc skb extension on allocation Function skbextadd() doesn't initialize created skb extension with any value and leaves it up to the user. However, since extension of type TCSKBEXT originally contained only…
When was CVE-2021-47136 disclosed?
CVE-2021-47136 was first published in the National Vulnerability Database on March 25, 2024, with the most recent update on March 13, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-47136 actively exploited?
CVE-2021-47136 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 14.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-47136?
CVE-2021-47136 has a CVSS v3 base score of 5.5 (NVD).
How do I remediate CVE-2021-47136?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-47136, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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