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CVE Record

CVE-2024-49884: ext4: fix slab-use-after-free in ext4_split_extent_at()

In the Linux kernel, the following vulnerability has been resolved: ext4: fix slab-use-after-free in ext4_split_extent_at() We hit the following use-after-free: ================================================================== BUG: KASAN: slab-use-after-free in ext4_split_extent_at+0xba8/0xcc0 Read of size 2 at addr ffff88810548ed08 by task kworker/u20:0/40 CPU: 0 PID: 40 Comm: kworker/u20:0 Not tainted 6.9.0-dirty #724 Call Trace: <TASK> kasan_report+0x93/0xc0 ext4_split_extent_at+0xba8/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Allocated by task 40: __kmalloc_noprof+0x1ac/0x480 ext4_find_extent+0xf3b/0x1e70 ext4_ext_map_blocks+0x188/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Freed by task 40: kfree+0xf1/0x2b0 ext4_find_extent+0xa71/0x1e70 ext4_ext_insert_extent+0xa22/0x3260 ext4_split_extent_at+0x3ef/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] ================================================================== The flow of issue triggering is as follows: ext4_split_extent_at path = *ppath ext4_ext_insert_extent(ppath) ext4_ext_create_new_leaf(ppath) ext4_find_extent(orig_path) path = *orig_path read_extent_tree_block // return -ENOMEM or -EIO ext4_free_ext_path(path) kfree(path) *orig_path = NULL a. If err is -ENOMEM: ext4_ext_dirty(path + path->p_depth) // path use-after-free !!! b. If err is -EIO and we have EXT_DEBUG defined: ext4_ext_show_leaf(path) eh = path[depth].p_hdr // path also use-after-free !!! So when trying to zeroout or fix the extent length, call ext4_find_extent() to update the path. In addition we use *ppath directly as an ext4_ext_show_leaf() input to avoid possible use-after-free when EXT_DEBUG is defined, and to avoid unnecessary path updates.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux ext4 filesystem flaw can access memory after it has been freed during certain write operations and error conditions. A locally authenticated, low-privileged attacker may be able to cause serious confidentiality, integrity, or availability impact. The supplied evidence does not establish active exploitation.

Executive priority

Treat this as a high-priority kernel maintenance issue, especially on shared systems offering local execution and using ext4. Schedule vendor-approved updates promptly. Emergency internet-edge action is not indicated by the local attack vector or current exploitation evidence, but delayed patching preserves a potentially high-impact kernel weakness.

Technical view

ext4_split_extent_at() can retain a stale extent path after ext4_find_extent() encounters ENOMEM or EIO, frees the path, and clears the original pointer. Later dirtying or EXT_DEBUG processing can read the freed slab object. Stable-kernel commits refresh the path and use the current pointer for debug output.

Likely exposure

Systems using ext4 on a listed affected Linux kernel branch are potential candidates. The CVSS vector indicates local, low-privileged access rather than direct network exploitation. Distribution backports may affect status, so compare the installed kernel package with vendor advisories and the applicable stable-kernel commit.

Exploitation context

The documented trigger involves ext4 writeback and unwritten-extent processing when extent lookup returns an out-of-memory or I/O error. No user interaction is required after local access. The CVE is not listed as KEV, and the supplied sources provide no evidence of active exploitation or public weaponization.

Researcher notes

KASAN demonstrated a two-byte read from a freed slab allocation. The vulnerable path follows ext4_ext_insert_extent() into ext4_find_extent(), where failure cleanup invalidates the caller's path. No CWE is supplied. The sources establish the memory-safety defect and fix, but do not demonstrate reliable privilege escalation or other exploitation.

Mitigation direction

  • Install a distribution kernel containing the applicable upstream stable fix, following vendor guidance.
  • For Debian LTS systems, consult the cited Debian security advisory before scheduling the kernel update.
  • Prioritize ext4 systems that permit untrusted users or workloads to execute locally.

Validation and detection

  • Inventory running kernel releases and identify systems mounting ext4 filesystems.
  • Compare each kernel package against its distribution advisory or the applicable stable fix commit.
  • After maintenance, confirm systems are running the updated kernel package.
  • Review kernel diagnostics for ext4 writeback faults or use-after-free reports.
Prepared
Confidence
high
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2024-49884 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
2ADP providers
12Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2024-49884Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxdfe5080939ea4686b3414b5d970a9b26733c57a4, dfe5080939ea4686b3414b5d970a9b26733c57a4, dfe5080939ea4686b3414b5d970a9b26733c57a4, dfe5080939ea4686b3414b5d970a9b26733c57a4, dfe5080939ea4686b3414b5d970a9b26733c57a4, dfe5080939ea4686b3414b5d970a9b26733c57a4, dfe5080939ea4686b3414b5d970a9b26733c57a4, dfe5080939ea4686b3414b5d970a9b26733c57a4, dfe5080939ea4686b3414b5d970a9b26733c57a4unaffected
LinuxLinux3.18, 0, 4.19.323, 5.4.290, 5.10.227, 5.15.168, 6.1.113, 6.6.55, 6.10.14, 6.11.3, 6.12affected
Weakness

CWE details

No CWE listed

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