CVE-2021-46955Network attack vector

Service interruption and stack disclosure via route miscast

Published Feb 27, 2024 · Updated Aug 5, 2026

An out-of-bounds read in Linux Open vSwitch IPv4 fragmentation allows remote attackers to disclose kernel stack data and interrupt service. ovs_fragment() supplies a temporary dst_entry to ip_do_fragment(), whose MTU path treats it as an rtable and reads rt_mtu_locked beyond the object. Reachability requires Open vSwitch to execute an IPv4 fragmentation action; the published network vector requires no authentication, and the bounded effects are stack-data disclosure and kernel service interruption.

CVSS severity8.2
High
EPSS probability0.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

An out-of-bounds read in Linux Open vSwitch IPv4 fragmentation allows remote attackers to disclose kernel stack data and interrupt service. ovs_fragment() supplies a temporary dst_entry to ip_do_fragment(), whose MTU path treats it as an rtable and reads rt_mtu_locked beyond the object. Reachability requires Open vSwitch to execute an IPv4 fragmentation action; the published network vector requires no authentication, and the bounded effects are stack-data disclosure and kernel service interruption.

The record

CVE
CVE-2021-46955
Published
Feb 27, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-125, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 27, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=119bbaa6795a4f4aed46994cc7d9ab01989c87e3 <b1d7280f9ba1bfdbc3af5bdb82e51f014854f26f
  2. Affected versionversion=3.16.57 <3.17
  3. Affected versionversion=4.14.45 <4.14.233
  4. Affected versionversion=4.16
  5. Affected versionversion=4.4.134 <4.4.269
  6. Affected versionversion=4.9.104 <4.9.269
  7. Affected versionversion=8387fbac8e18e26a60559adc63e0b7067303b0a4 <5a52fa8ad45b5a593ed416adf326538638454ff1
  8. Affected versionversion=d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 <490ad0a2390442d0a7b8c00972a83dbb09cab142
  9. Affected versionversion=d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 <7c0ea5930c1c211931819d83cfb157bff1539a4c
  10. Affected versionversion=d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 <a1478374b0bda89b4277a8afd39208271faad4be
  11. Affected versionversion=d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 <b3502b04e84ac5349be95fc033c17bd701d2787a
  12. Affected versionversion=d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 <d841d3cf5297fde4ce6a41ff35451d0e82917f3e
  13. Affected versionversion=d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 <df9e900de24637be41879e2c50afb713ec4e8b2e
  14. Affected versionversion=d543907a4730400f5c5b684c57cb5bbbfd6136ab <23e17ec1a5eb53fe39cc34fa5592686d5acd0dac
  15. Affected versionversion=df9ece1148e2ec242871623dedb004f7a1387125

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=119bbaa6795a4f4aed46994cc7d9ab01989c87e3 <b1d7280f9ba1bfdbc3af5bdb82e51f014854f26f; version=3.16.57 <3.17; version=4.14.45 <4.14.233; version=4.16; version=4.4.134 <4.4.269; version=4.9.104 <4.9.269; version=8387fbac8e18e26a60559adc63e0b7067303b0a4 <5a52fa8ad45b5a593ed416adf326538638454ff1; version=d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 <490ad0a2390442d0a7b8c00972a83dbb09cab142; version=d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 <7c0ea5930c1c211931819d83cfb157bff1539a4c; version=d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 <a1478374b0bda89b4277a8afd39208271faad4be; version=d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 <b3502b04e84ac5349be95fc033c17bd701d2787a; version=d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 <d841d3cf5297fde4ce6a41ff35451d0e82917f3e; version=d52e5a7e7ca49457dd31fc8b42fb7c0d58a31221 <df9e900de24637be41879e2c50afb713ec4e8b2e; version=d543907a4730400f5c5b684c57cb5bbbfd6136ab <23e17ec1a5eb53fe39cc34fa5592686d5acd0dac; version=df9ece1148e2ec242871623dedb004f7a1387125

Published CVSS scores

8.2kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
7.1NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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