CVE-2026-74635— Linux kernel 安全漏洞
一分钟漏洞结论
影响对象
Linux Linux
利用判断
尚无明确在野利用证据，仍需结合暴露面评估
建议动作
优先检查厂商安全公告和参考链接中的修复版本；无法立即升级时，限制受影响服务暴露并加强监测。
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel 6.18版本存在安全漏洞，该漏洞源于bit_cursor()函数未对字形索引进行边界检查，屏幕缓冲区值可能大于当前字体字形计数，攻击者可通过vcs_write()向/dev/vcsa写入任意16位值触发，可能导致越界读取。
可能的 ATT&CK 技术 1 AI
T1068 · Exploitation for Privilege Escalation影响版本矩阵 27
| 厂商 | 产品 | 版本范围 | 状态 |
|---|---|---|---|
| Linux | Linux | 0998a6cb232674408a03e8561dc15aa266b2f53b< 250159ace2dc53c1bdad267aa8da51b638748700 |
affected |
db5c9a162d2f42bcc842b76b3d935dcc050a0eec< 46336f476484f36145e5117e72d7b590f47433ee |
affected | ||
c12003bf91fdff381c55ef54fef3e961a5af2545< bf750cfeacf4e47ac72dadc7f05839696efb8576 |
affected | ||
9ba1a7802ca9a2590cef95b253e6526f4364477f< 94134d70abf9273b70499d97d0adc9185ef21091 |
affected | ||
901f44227072be60812fe8083e83e1533c04eed1< c1e7351767dd30fc574395c82121e4c67b882da3 |
affected | ||
18c4ef4e765a798b47980555ed665d78b71aeadf< bc9db0d879c655d5dfd8add32fd60f13e65d132c |
affected | ||
18c4ef4e765a798b47980555ed665d78b71aeadf< 9ea879862e66e354e616028c31b39aa3eb6d35d8 |
affected | ||
18c4ef4e765a798b47980555ed665d78b71aeadf< e033cbf3975a8465f879ebd5989dc35b04423a4d |
affected | ||
| … +19 条更多 | |||
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一、 漏洞 CVE-2026-74635 基础信息
漏洞信息
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Vulnerability Title
fbdev: bitblit: bound-check glyph index in bit_cursor()
来源: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved:
fbdev: bitblit: bound-check glyph index in bit_cursor()
bit_cursor() fetches the glyph under the cursor with
c = scr_readw(vc_pos);
src = vc_font.data + ((c & charmask) * w * height);
where charmask is 0x1ff when vc_hi_font_mask is set. The screen buffer
value comes directly from scr_readw() and may be larger than the current
font's glyph count.
Syzkaller triggers this via vcs_write(). The Call Trace shows
vcs_write() in vc_screen.c writing an arbitrary 16-bit value with
writev() to /dev/vcsa, which vcs_write_buf() in vc_screen.c stores via
vcs_scr_writew() without checking charcount. The stored value is later
read in bit_cursor() in bitblit.c.
When the font is changed from a font with 512 glyphs to a font with
256 glyphs, the screen buffer can retain characters with the high
bit set from the previous mode, which could also produce the same
out-of-bounds access.
BUG: KASAN: global-out-of-bounds in soft_cursor+0x378/0x6bc drivers/video/fbdev/core/softcursor.c:70
Read of size 16 at addr ffff800086c57970
Call Trace:
soft_cursor+0x378/0x6bc drivers/video/fbdev/core/softcursor.c:70
bit_cursor+0xa90/0x1108 drivers/video/fbdev/core/bitblit.c:365
fbcon_cursor+0x344/0x498 drivers/video/fbdev/core/fbcon.c:1427
hide_cursor+0xdc/0x2d0 drivers/tty/vt/vt.c:883
update_region+0x100/0x18c drivers/tty/vt/vt.c:669
vcs_write+0x8ec/0xaf0 drivers/tty/vt/vc_screen.c:685
bit_putcs_aligned() and bit_putcs_unaligned() already clamp the glyph
index to vc_font.charcount. Apply the same clamp in bit_cursor() after
extracting the attribute and masking, before indexing fontdata.
The fix completes the bounds checking started in commit 18c4ef4e765a
("fbdev: bitblit: bound-check glyph index in bit_putcs*"), which missed
the cursor path.
This change should be safe because the clamp reuses the existing
contract from fbcon: charcount is maintained under console_lock in
con_font_set() and fbcon_font_set(), and hi_font_mask is cleared when
switching from 512 to 256 glyphs. When stale screen data with high bits
remains after a font switch, or when vcs_write() stores an arbitrary
value, clamping the index to 0 prevents the out-of-bounds read without
changing cursor semantics — the same fallback bit_putcs uses.
来源: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
来源: CVE Program / CVE List V5
Vulnerability Type
N/A
来源: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
来源: 中国国家信息安全漏洞库 CNNVD
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel 6.18版本存在安全漏洞，该漏洞源于bit_cursor()函数未对字形索引进行边界检查，屏幕缓冲区值可能大于当前字体字形计数，攻击者可通过vcs_write()向/dev/vcsa写入任意16位值触发，可能导致越界读取。
来源: 中国国家信息安全漏洞库 CNNVD
CVSS Information
N/A
来源: 中国国家信息安全漏洞库 CNNVD
Vulnerability Type
N/A
来源: 中国国家信息安全漏洞库 CNNVD
受影响产品
二、漏洞 CVE-2026-74635 的公开POC
| # | POC 描述 | 源链接 | 神龙链接 |
|---|
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CVE-2026-74635 补丁与修复 (8)
同批安全公告 · Linux · 2026-08-22 · 共 149 条
| CVE-2026-74612 | 10.0 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74705 | 10.0 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74628 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74688 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74617 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74616 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74611 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74608 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74723 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74662 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74727 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74597 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74591 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74586 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74587 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74588 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74669 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74730 | 9.8 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74712 | 9.3 CRITICAL | Linux kernel 安全漏洞 |
| CVE-2026-74665 | 9.1 CRITICAL | Linux kernel 安全漏洞 |
显示前 20 条，共 149 条。 查看全部 → →
IV. Related Vulnerabilities
V. Comments for CVE-2026-74635
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