CVE-2021-47656
7.8 · HIGHOverview
CVE-2021-47656 is a high-severity vulnerability affecting linux linux_kernel. It was published on February 26, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).
This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. No authentication or special privileges are required for exploitation.
Technical Description
In the Linux kernel, the following vulnerability has been resolved:
jffs2: fix use-after-free in jffs2_clear_xattr_subsystem
When we mount a jffs2 image, assume that the first few blocks of
the image are normal and contain at least one xattr-related inode,
but the next block is abnormal. As a result, an error is returned
in jffs2_scan_eraseblock(). jffs2_clear_xattr_subsystem() is then
called in jffs2_build_filesystem() and then again in
jffs2_do_fill_super().
Finally we can observe the following report:
==================================================================
BUG: KASAN: use-after-free in jffs2_clear_xattr_subsystem+0x95/0x6ac
Read of size 8 at addr ffff8881243384e0 by task mount/719
Call Trace:
dump_stack+0x115/0x16b
jffs2_clear_xattr_subsystem+0x95/0x6ac
jffs2_do_fill_super+0x84f/0xc30
jffs2_fill_super+0x2ea/0x4c0
mtd_get_sb+0x254/0x400
mtd_get_sb_by_nr+0x4f/0xd0
get_tree_mtd+0x498/0x840
jffs2_get_tree+0x25/0x30
vfs_get_tree+0x8d/0x2e0
path_moun
Remediation
Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| linux | linux_kernel | >= 2.6.18, < 4.9.311 | Affected |
References
Frequently Asked Questions
What is CVE-2021-47656?
CVE-2021-47656 is a high-severity vulnerability affecting linux linux_kernel. It was published on February 26, 2025 and has a CVSS 3.1 base score of 7.8 (HIGH).
How severe is CVE-2021-47656?
This vulnerability has a CVSS 3.1 base score of 7.8, rated HIGH. It requires local or adjacent network access to exploit. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2021-47656?
Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2021-47656?
CyberStrike's AI-powered security agents can automatically detect CVE-2021-47656 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
Automated penetration testing that runs continuously, not just quarterly.
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