CVE-2021-46955

HIGHNVD 7.17.1—
EchelonGraph scoreMEDIUM confidence

Score 7.1 from GitHub Security Advisory (severity: HIGH) published 2024-02-27. NVD baseline CVSS 7.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 4 sources updated this week
7.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 7.1Exploit: None knownExposed: 0

A fix is available — apply it.

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

openvswitch: fix stack OOB read while fragmenting IPv4 packets

running openvswitch on kernels built with KASAN, it's possible to see the following splat while testing fragmentation of IPv4 packets:

BUG: KASAN: stack-out-of-bounds in ip_do_fragment+0x1b03/0x1f60 Read of size 1 at addr ffff888112fc713c by task handler2/1367

CPU: 0 PID: 1367 Comm: handler2 Not tainted 5.12.0-rc6+ #418 Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014 Call Trace: dump_stack+0x92/0xc1 print_address_description.constprop.7+0x1a/0x150 kasan_report.cold.13+0x7f/0x111 ip_do_fragment+0x1b03/0x1f60 ovs_fragment+0x5bf/0x840 [openvswitch] do_execute_actions+0x1bd5/0x2400 [openvswitch] ovs_execute_actions+0xc8/0x3d0 [openvswitch] ovs_packet_cmd_execute+0xa39/0x1150 [openvswitch] genl_family_rcv_msg_doit.isra.15+0x227/0x2d0 genl_rcv_msg+0x287/0x490 netlink_rcv_skb+0x120/0x380 genl_rcv+0x24/0x40 netlink_unicast+0x439/0x630 netlink_sendmsg+0x719/0xbf0 sock_sendmsg+0xe2/0x110 ____sys_sendmsg+0x5ba/0x890 ___sys_sendmsg+0xe9/0x160 __sys_sendmsg+0xd3/0x170 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f957079db07 Code: c3 66 90 41 54 41 89 d4 55 48 89 f5 53 89 fb 48 83 ec 10 e8 eb ec ff ff 44 89 e2 48 89 ee 89 df 41 89 c0 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 48 89 44 24 08 e8 24 ed ff ff 48 RSP: 002b:00007f956ce35a50 EFLAGS: 00000293 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000000000019 RCX: 00007f957079db07 RDX: 0000000000000000 RSI: 00007f956ce35ae0 RDI: 0000000000000019 RBP: 00007f956ce35ae0 R08: 0000000000000000 R09: 00007f9558006730 R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000 R13: 00007f956ce37308 R14: 00007f956ce35f80 R15: 00007f956ce35ae0

The buggy address belongs to the page: page:00000000af2a1d93 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x112fc7 flags: 0x17ffffc0000000() raw: 0017ffffc0000000 0000000000000000 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected

addr ffff888112fc713c is located in stack of task handler2/1367 at offset 180 in frame: ovs_fragment+0x0/0x840 [openvswitch]

this frame has 2 objects: [32, 144) 'ovs_dst' [192, 424) 'ovs_rt'

Memory state around the buggy address: ffff888112fc7000: f3 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888112fc7080: 00 f1 f1 f1 f1 00 00 00 00 00 00 00 00 00 00 00 >ffff888112fc7100: 00 00 00 f2 f2 f2 f2 f2 f2 00 00 00 00 00 00 00 ^ ffff888112fc7180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888112fc7200: 00 00 00 00 00 00 f2 f2 f2 00 00 00 00 00 00 00

for IPv4 packets, ovs_fragment() uses a temporary struct dst_entry. Then, in the following call graph:

ip_do_fragment() ip_skb_dst_mtu() ip_dst_mtu_maybe_forward() ip_mtu_locked()

the pointer to struct dst_entry is used as pointer to struct rtable: this turns the access to struct members like rt_mtu_locked into an OOB read in the stack. Fix this changing the temporary variable used for IPv4 packets in ovs_fragment(), similarly to what is done for IPv6 few lines below.

CVSS v3
7.1
EG Score
7.1(medium)
EG Risk
32(Track)
EG Risk 32/100SSVC: 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
Severity71% × 45%
Exploitation1% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
51%
KEV
Not listed

Published

February 27, 2024

Last Modified

August 5, 2026

Advisory Details (9)

Auto-updated Aug 5, 2026
No patch confirmed yet.
generic

openvswitch: fix stack OOB read while fragmenting IPv4 packets - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/7c0ea5930c1c211931819d83cfb157bff1539a4c
generic

openvswitch: fix stack OOB read while fragmenting IPv4 packets - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/b3502b04e84ac5349be95fc033c17bd701d2787a
generic

openvswitch: fix stack OOB read while fragmenting IPv4 packets - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/d841d3cf5297fde4ce6a41ff35451d0e82917f3e
generic

openvswitch: fix stack OOB read while fragmenting IPv4 packets - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/a1478374b0bda89b4277a8afd39208271faad4be
generic

openvswitch: fix stack OOB read while fragmenting IPv4 packets - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/490ad0a2390442d0a7b8c00972a83dbb09cab142
generic

openvswitch: fix stack OOB read while fragmenting IPv4 packets - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/df9e900de24637be41879e2c50afb713ec4e8b2e
generic

openvswitch: fix stack OOB read while fragmenting IPv4 packets - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/5a52fa8ad45b5a593ed416adf326538638454ff1
generic

openvswitch: fix stack OOB read while fragmenting IPv4 packets - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/23e17ec1a5eb53fe39cc34fa5592686d5acd0dac
generic

openvswitch: fix stack OOB read while fragmenting IPv4 packets - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/b1d7280f9ba1bfdbc3af5bdb82e51f014854f26f

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntulinux-virtual-lts-xenial (4.4.0.253.259) @ xenial2026-05-24ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

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

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 15× in last 7d / 48× 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 126 total refreshes for this CVE.

  1. 2026-08-07 16:24 UTCEPSS rescore
  2. 2026-08-06 13:44 UTCEPSS rescore
  3. 2026-08-05 19:15 UTCEPSS rescore
  4. 2026-08-05 09:46 UTCEG score recompute
  5. 2026-08-05 09:46 UTCGHSA enrichment
  6. 2026-08-04 15:06 UTCEPSS rescore
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  8. 2026-08-04 12:22 UTCVendor advisory
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  10. 2026-08-04 10:34 UTCEPSS rescore
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  1. 2026-07-23 02:06 UTCEG score recompute
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  45. 2026-06-25 13:48 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2021-46955?
CVE-2021-46955 is a high vulnerability published on February 27, 2024. In the Linux kernel, the following vulnerability has been resolved: openvswitch: fix stack OOB read while fragmenting IPv4 packets running openvswitch on kernels built with KASAN, it's possible to see the following splat while testing fragmentation of IPv4 packets: BUG: KASAN: stack-out-of-bounds…
When was CVE-2021-46955 disclosed?
CVE-2021-46955 was first published in the National Vulnerability Database on February 27, 2024, with the most recent update on August 5, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-46955 actively exploited?
CVE-2021-46955 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 48.8% of all scored CVEs.
What is the CVSS score of CVE-2021-46955?
CVE-2021-46955 has a CVSS v3 base score of 7.1 (NVD).
How do I remediate CVE-2021-46955?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-46955, 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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