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CVE-2021-47656

7.8 · HIGH

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 i…

Published Feb 26, 2025CWE-416EPSS 0.26%

Overview

CVE-2021-47656 is a high-severity vulnerability. 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, patches, and mitigation guidance. 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.

References

Refgit.kernel.org/stable/c/22327bd7988f21de3a53c1373f3b81542bfe1f44Refgit.kernel.org/stable/c/30bf7244acf32f19cb722c39f7bc1c2a9f300422Refgit.kernel.org/stable/c/3bd2454162ec6bbb5503233c804fce6e4b6dcec5Refgit.kernel.org/stable/c/4c7c44ee1650677fbe89d86edbad9497b7679b5cRefgit.kernel.org/stable/c/7a75740206af5f17e9f3efa384211cba70213da1Refgit.kernel.org/stable/c/7bb7428dd73991bf4b3a7a61b493ca50046c2b13Refgit.kernel.org/stable/c/8c0f024f29e055840a5a89fe23b96ae3f921afedRefgit.kernel.org/stable/c/9150cb625b46f68d524f4cfd491f1aafc23e10a9Refgit.kernel.org/stable/c/c3b07c875fa8f906f932976460fd14798596f101

How CyberStrike helps

Frequently asked questions

What is CVE-2021-47656?

CVE-2021-47656 is a high-severity vulnerability. 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, patches, and mitigation guidance. 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 is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-47656 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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