CVE-2021-33033: linux linux_kernel Use After Free

Analyzed

AliasesUBUNTU-CVE-2021-33033DEBIAN-CVE-2021-33033

Published 14-05-2021Last modified 03-08-2024

Vulnerability summary

CVE-2021-33033 is a high (CVSS 7.8) Use After Free vulnerability in linux linux_kernel. EPSS estimates a 0.57% chance of exploitation in the next 30 days, higher than 47.2% of scored vulnerabilities. 2 public exploits are recorded.

Priority

Prioritisepublic exploit

Public exploit (reference, Date unknown)

Source freshness unavailable

How is this decided?

CVSS score

7.8/10

010

High · v3.1 (NVD)

EPSS score

0.57%

0%100%

Low · 0.00 pp in 30 days

KEVNot listedNot listed by any tracked catalog.

RansomwareNot flaggedNo ransomware use recorded.

Public exploits2reference

Timeline

14-05-2021
PublishedVulnerability first disclosed.
03-08-2024
Last modifiedVulnerability information updated.

Description

The Linux kernel before 5.11.14 has a use-after-free in cipso_v4_genopt in net/ipv4/cipso_ipv4.c because the CIPSO and CALIPSO refcounting for the DOI definitions is mishandled, aka CID-ad5d07f4a9cd. This leads to writing an arbitrary value.

CVSS metrics

4 scores · 3 sources · 2 versions

v3.17.8v2.04.6

EPSS trend

Probability

0.57%

Chance of exploitation in the next 30 days

Percentile

47%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.57% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs

CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

2 found

referenceUnverified
Exploit Reference (syzkaller.appspot.com)
Maturity: unknown
referenceUnverified
Exploit Reference (sites.google.com)
Maturity: unknown

Weaknesses

CWE · root cause

CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu48 products

linuxAll versions (No fix recorded) | < 4.4.0-222.255 | < 4.15.0-144.148 | < 5.4.0-73.82
linux-aws< 4.4.0-1102.107 | < 4.4.0-1138.152 | < 4.15.0-1103.110 | < 5.4.0-1048.50
linux-aws-5.0All versions (No fix recorded)
linux-aws-5.3All versions (No fix recorded)
linux-aws-5.4< 5.4.0-1048.50~18.04.1

linux-aws-fips< 4.15.0-2045.47 | All versions (No fix recorded) | < 5.4.0-1069.73+fips2
linux-aws-hwe< 4.15.0-1103.110~16.04.1
linux-azure< 4.15.0-1115.128~14.04.1 | < 4.15.0-1115.128~16.04.1 | All versions (No fix recorded) | < 5.4.0-1047.49
linux-azure-4.15< 4.15.0-1115.128
linux-azure-5.3All versions (No fix recorded)
linux-azure-5.4< 5.4.0-1047.49~18.04.1
linux-azure-edgeAll versions (No fix recorded)
linux-azure-fips< 4.15.0-2027.30 | All versions (No fix recorded) | < 5.4.0-1073.76+fips1
linux-dell300x< 4.15.0-1022.26
linux-fips< 4.4.0-1072.78 | All versions (No fix recorded) | < 4.15.0-1060.68
linux-gcp< 4.15.0-1100.113~16.04.1 | All versions (No fix recorded) | < 5.4.0-1043.46
linux-gcp-4.15< 4.15.0-1100.113
linux-gcp-5.3All versions (No fix recorded)
linux-gcp-5.4< 5.4.0-1043.46~18.04.1
linux-gcp-edgeAll versions (No fix recorded)
linux-gcp-fipsAll versions (No fix recorded) | < 5.4.0-1067.71~20.04.1
linux-gke< 5.4.0-1043.45
linux-gke-4.15All versions (No fix recorded)
linux-gke-5.4< 5.4.0-1043.45~18.04.1
linux-gkeop< 5.4.0-1015.16
linux-gkeop-5.4< 5.4.0-1015.16~18.04.1
linux-hwe< 4.15.0-144.148~16.04.1 | All versions (No fix recorded)
linux-hwe-5.4< 5.4.0-73.82~18.04.1
linux-hwe-5.8< 5.8.0-55.62~20.04.1
linux-hwe-edgeAll versions (No fix recorded)
linux-intel-iot-realtimeAll versions (No fix recorded)
linux-kvm< 4.4.0-1103.112 | < 4.15.0-1092.94 | < 5.4.0-1039.40
linux-lts-xenial< 4.4.0-222.255~14.04.1
linux-oemAll versions (No fix recorded)
linux-oem-5.10< 5.10.0-1021.22
linux-oem-5.6All versions (No fix recorded)
linux-oracle< 4.15.0-1072.80~16.04.1 | < 4.15.0-1072.80 | < 5.4.0-1045.49
linux-oracle-5.0All versions (No fix recorded)
linux-oracle-5.3All versions (No fix recorded)
linux-oracle-5.4< 5.4.0-1044.47~18.04.1
linux-raspi< 5.4.0-1035.38
linux-raspi-5.4< 5.4.0-1035.38~18.04.1
linux-raspi-realtimeAll versions (No fix recorded)
linux-raspi2< 4.15.0-1086.91 | All versions (No fix recorded)
linux-realtimeAll versions (No fix recorded)
linux-riscvAll versions (No fix recorded)
linux-riscv-5.8< 5.8.0-26.28~20.04.1
linux-snapdragon< 4.15.0-1103.112

Show all 48

Debian1 product

linux< 5.10.24-1

Linux1 product

linux_kernel≥ 2.6.28, < 4.9.298 | ≥ 4.10, < 4.14.226 | ≥ 4.15, < 4.19.181 | ≥ 4.20, < 5.4.106 | ≥ 5.5, < 5.10.24 | ≥ 5.11, < 5.11.7

3 vendors · 50 products

References

15 links

cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.7X Refsource MISCREPORTMailing ListPatchVendor Advisory
syzkaller.appspot.com/bug?id=96e7d345748d8814901c91cd92084ed04b46701eX Refsource MISCREPORTExploitMailing ListThird Party Advisory
sites.google.com/view/syzscope/kasan-use-after-free-read-in-cipso_v4_genoptX Refsource MISCREPORTExploitThird Party Advisory
git.kernel.org/pub/…X Refsource MISCMailing ListPatchVendor Advisory
git.kernel.org/pub/…X Refsource MISCMailing ListPatchVendor Advisory
cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.14X Refsource MISCREPORTMailing ListPatchVendor Advisory
ubuntu.com/security/CVE-2021-33033REPORT
git.kernel.org/linus/ad5d07f4a9cd671233ae20983848874731102c08REPORT
git.kernel.org/linus/1165affd484889d4986cf3b724318935a0b120d8REPORT
ubuntu.com/security/notices/USN-4979-1Advisory

Show all 15 references

ubuntu.com/security/notices/USN-4984-1Advisory
ubuntu.com/security/notices/USN-5343-1Advisory
www.cve.org/CVERecord?id=CVE-2021-33033REPORT
security-tracker.debian.org/tracker/CVE-2021-33033Advisory
nvd.nist.gov/vuln/detail/CVE-2021-33033OvalAdvisory