Linux: Use After Free
CVE-2024-49883 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions e17ebe4fdd7665c93ae9459ba40fcdfb76769ac1, 975ca06f3fd154c5f7742083e7b2574c57d1c0c3, 5e811066c5ab709b070659197dccfb80ab650ddd as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.28% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to e17ebe4fdd7665c93ae9459ba40fcdfb76769ac1 or 975ca06f3fd154c5f7742083e7b2574c57d1c0c3 or 5e811066c5ab709b070659197dccfb80ab650ddd or 9df59009dfc6d9fc1bd9ddf6c5ab6e56d6ed887a, whichever matches your release line, or a later version.
- Update Linux Kernel to 4.19.323 or 5.4.285 or 5.10.227 or 5.15.168, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 10809df84a4d868db61af621bae3658494165279 up to, but not including, e17ebe4fdd7665c93ae9459ba40fcdfb76769ac1; 10809df84a4d868db61af621bae3658494165279 up to, but not including, 975ca06f3fd154c5f7742083e7b2574c57d1c0c3; 10809df84a4d868db61af621bae3658494165279 up to, but not including, 5e811066c5ab709b070659197dccfb80ab650ddd; 10809df84a4d868db61af621bae3658494165279 up to, but not including, 9df59009dfc6d9fc1bd9ddf6c5ab6e56d6ed887a; 10809df84a4d868db61af621bae3658494165279 up to, but not including, 51db04892a993cace63415be99848970a0f15ef2; 10809df84a4d868db61af621bae3658494165279 up to, but not including, 8162ee5d94b8c0351be0a9321be134872a7654a1; 10809df84a4d868db61af621bae3658494165279 up to, but not including, beb7b66fb489041c50c6473100b383f7a51648fc; 10809df84a4d868db61af621bae3658494165279 up to, but not including, bfed082ce4b1ce6349b05c09a0fa4f3da35ecb1b; and 2 more ranges | e17ebe4fdd7665c93ae9459ba40fcdfb76769ac1, 975ca06f3fd154c5f7742083e7b2574c57d1c0c3, 5e811066c5ab709b070659197dccfb80ab650ddd, 9df59009dfc6d9fc1bd9ddf6c5ab6e56d6ed887a, 51db04892a993cace63415be99848970a0f15ef2, 8162ee5d94b8c0351be0a9321be134872a7654a1 |
| Debian | Debian Linux | 11.0 | Not stated |
| Linux | Linux Kernel | 3.18 up to, but not including, 4.19.323; 4.20 up to, but not including, 5.4.285; 5.5 up to, but not including, 5.10.227; 5.11 up to, but not including, 5.15.168; 5.16 up to, but not including, 6.1.113; 6.2 up to, but not including, 6.6.55; 6.7 up to, but not including, 6.10.14; 6.11 up to, but not including, 6.11.3 | 4.19.323, 5.4.285, 5.10.227, 5.15.168, 6.1.113, 6.6.55 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: ext4: aovid use-after-free in ext4_ext_insert_extent() As Ojaswin mentioned in Link, in ext4_ext_insert_extent(), if the path is reallocated in ext4_ext_create_new_leaf(), we'll use the stale path and cause UAF. Below is a sample trace with dummy values: ext4_ext_insert_extent path = *ppath = 2000 ext4_ext_create_new_leaf(ppath) ext4_find_extent(ppath) path = *ppath = 2000 if (depth > path[0].p_maxdepth) kfree(path = 2000); *ppath = path = NULL; path = kcalloc() = 3000 *ppath = 3000; return path; /* here path is still 2000, UAF! */ eh = path[depth].p_hdr ================================================================== BUG: KASAN: slab-use-after-free in ext4_ext_insert_extent+0x26d4/0x3330 Read of size 8 at addr ffff8881027bf7d0 by task kworker/u36:1/179 CPU: 3 UID: 0 PID: 179 Comm: kworker/u6:1 Not tainted 6.11.0-rc2-dirty #866 Call Trace: <TASK> ext4_ext_insert_extent+0x26d4/0x3330 ext4_ext_map_blocks+0xe22/0x2d40 ext4_map_blocks+0x71e/0x1700 ext4_do_writepages+0x1290/0x2800 [...] Allocated by task 179: ext4_find_extent+0x81c/0x1f70 ext4_ext_map_blocks+0x146/0x2d40 ext4_map_blocks+0x71e/0x1700 ext4_do_writepages+0x1290/0x2800 ext4_writepages+0x26d/0x4e0 do_writepages+0x175/0x700 [...] Freed by task 179: kfree+0xcb/0x240 ext4_find_extent+0x7c0/0x1f70 ext4_ext_insert_extent+0xa26/0x3330 ext4_ext_map_blocks+0xe22/0x2d40 ext4_map_blocks+0x71e/0x1700 ext4_do_writepages+0x1290/0x2800 ext4_writepages+0x26d/0x4e0 do_writepages+0x175/0x700 [...] ================================================================== So use *ppath to update the path to avoid the above problem.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The 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.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/51db04892a993cace63415be99848970a0f15ef2
- git.kernel.org/stable/c/5e811066c5ab709b070659197dccfb80ab650ddd
- git.kernel.org/stable/c/8162ee5d94b8c0351be0a9321be134872a7654a1
- git.kernel.org/stable/c/975ca06f3fd154c5f7742083e7b2574c57d1c0c3
- git.kernel.org/stable/c/9df59009dfc6d9fc1bd9ddf6c5ab6e56d6ed887a
- git.kernel.org/stable/c/a164f3a432aae62ca23d03e6d926b122ee5b860d
- git.kernel.org/stable/c/beb7b66fb489041c50c6473100b383f7a51648fc
- git.kernel.org/stable/c/bfed082ce4b1ce6349b05c09a0fa4f3da35ecb1b
- git.kernel.org/stable/c/e17ebe4fdd7665c93ae9459ba40fcdfb76769ac1
Third-party and government advisories
- lists.debian.org/debian-lts-announce/2025/01/msg00001.htmlMailing List, Third Party Advisory
- lists.debian.org/debian-lts-announce/2025/03/msg00002.htmlMailing List, Third Party Advisory
Recent Use After Free vulnerabilities
- 7.0 High severity
- 7.0 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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