Linux: Double Free
CVE-2024-49882 is a high-severity double 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 d4574bda63906bf69660e001470bfe1a0ac524ae, f9fd47c9d9548f9e47fa60098eab99dde175401d, b6c29c8f3d7cb67b505f3b2f6c242d52298d1f2e 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 0.32% 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 d4574bda63906bf69660e001470bfe1a0ac524ae or f9fd47c9d9548f9e47fa60098eab99dde175401d or b6c29c8f3d7cb67b505f3b2f6c242d52298d1f2e or 32bbb59e3f18facd7201bef110010bf35819b8c3, 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 | ecb94f5fdf4b72547fca022421a9dca1672bddd4 up to, but not including, d4574bda63906bf69660e001470bfe1a0ac524ae; ecb94f5fdf4b72547fca022421a9dca1672bddd4 up to, but not including, f9fd47c9d9548f9e47fa60098eab99dde175401d; ecb94f5fdf4b72547fca022421a9dca1672bddd4 up to, but not including, b6c29c8f3d7cb67b505f3b2f6c242d52298d1f2e; ecb94f5fdf4b72547fca022421a9dca1672bddd4 up to, but not including, 32bbb59e3f18facd7201bef110010bf35819b8c3; ecb94f5fdf4b72547fca022421a9dca1672bddd4 up to, but not including, 78bbc3d15b6f443acb26e94418c445bac940d414; ecb94f5fdf4b72547fca022421a9dca1672bddd4 up to, but not including, 68a69cf60660c73990c1875f94a5551600b04775; ecb94f5fdf4b72547fca022421a9dca1672bddd4 up to, but not including, 7633407ca4ab8be2916ab214eb44ccebc6a50e1a; ecb94f5fdf4b72547fca022421a9dca1672bddd4 up to, but not including, 230ee0535d01478bad9a3037292043f39b9be10b; and 2 more ranges | d4574bda63906bf69660e001470bfe1a0ac524ae, f9fd47c9d9548f9e47fa60098eab99dde175401d, b6c29c8f3d7cb67b505f3b2f6c242d52298d1f2e, 32bbb59e3f18facd7201bef110010bf35819b8c3, 78bbc3d15b6f443acb26e94418c445bac940d414, 68a69cf60660c73990c1875f94a5551600b04775 |
| Debian | Debian Linux | 11.0 | Not stated |
| Linux | Linux Kernel | 3.7 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: fix double brelse() the buffer of the extents path In ext4_ext_try_to_merge_up(), set path[1].p_bh to NULL after it has been released, otherwise it may be released twice. An example of what triggers this is as follows: split2 map split1 |--------|-------|--------| ext4_ext_map_blocks ext4_ext_handle_unwritten_extents ext4_split_convert_extents // path->p_depth == 0 ext4_split_extent // 1. do split1 ext4_split_extent_at |ext4_ext_insert_extent | ext4_ext_create_new_leaf | ext4_ext_grow_indepth | le16_add_cpu(&neh->eh_depth, 1) | ext4_find_extent | // return -ENOMEM |// get error and try zeroout |path = ext4_find_extent | path->p_depth = 1 |ext4_ext_try_to_merge | ext4_ext_try_to_merge_up | path->p_depth = 0 | brelse(path[1].p_bh) ---> not set to NULL here |// zeroout success // 2. update path ext4_find_extent // 3. do split2 ext4_split_extent_at ext4_ext_insert_extent ext4_ext_create_new_leaf ext4_ext_grow_indepth le16_add_cpu(&neh->eh_depth, 1) ext4_find_extent path[0].p_bh = NULL; path->p_depth = 1 read_extent_tree_block ---> return err // path[1].p_bh is still the old value ext4_free_ext_path ext4_ext_drop_refs // path->p_depth == 1 brelse(path[1].p_bh) ---> brelse a buffer twice Finally got the following WARRNING when removing the buffer from lru: ============================================ VFS: brelse: Trying to free free buffer WARNING: CPU: 2 PID: 72 at fs/buffer.c:1241 __brelse+0x58/0x90 CPU: 2 PID: 72 Comm: kworker/u19:1 Not tainted 6.9.0-dirty #716 RIP: 0010:__brelse+0x58/0x90 Call Trace: <TASK> __find_get_block+0x6e7/0x810 bdev_getblk+0x2b/0x480 __ext4_get_inode_loc+0x48a/0x1240 ext4_get_inode_loc+0xb2/0x150 ext4_reserve_inode_write+0xb7/0x230 __ext4_mark_inode_dirty+0x144/0x6a0 ext4_ext_insert_extent+0x9c8/0x3230 ext4_ext_map_blocks+0xf45/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] ============================================
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Double Free
The product calls free() twice on the same memory address.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- Ensure that each allocation is freed only once. After freeing a chunk, set the pointer to NULL to ensure the pointer cannot be freed again. In complicated error conditions, be sure that clean-up routines respect the state of allocation properly. If the language is object oriented, ensure that object destructors delete each chunk of memory only once.
- Use a static analysis tool to find double free instances.
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/230ee0535d01478bad9a3037292043f39b9be10b
- git.kernel.org/stable/c/32bbb59e3f18facd7201bef110010bf35819b8c3
- git.kernel.org/stable/c/68a69cf60660c73990c1875f94a5551600b04775
- git.kernel.org/stable/c/7633407ca4ab8be2916ab214eb44ccebc6a50e1a
- git.kernel.org/stable/c/78bbc3d15b6f443acb26e94418c445bac940d414
- git.kernel.org/stable/c/b6c29c8f3d7cb67b505f3b2f6c242d52298d1f2e
- git.kernel.org/stable/c/d4574bda63906bf69660e001470bfe1a0ac524ae
- git.kernel.org/stable/c/dcaa6c31134c0f515600111c38ed7750003e1b9c
- git.kernel.org/stable/c/f9fd47c9d9548f9e47fa60098eab99dde175401d
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 Double Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 9.8 Critical severity
- 7.5 High severity
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