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CVE-2025-21922— ppp: Fix KMSAN uninit-value warning with bpf

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于未初始化PPP BPF程序头。

AI Predicted 3.3 Difficulty: Hard EPSS 0.23% · P13

Possible ATT&CK Techniques 1 AI

T1059 · Command and Scripting Interpreter

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< d685096c8129c9a92689975193e268945fd21dbf affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 2f591cb158807bdcf424f66f1fbfa6e4e50f3757 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 4e2191b0fd0c064d37b0db67396216f2d4787e0f affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 3de809a768464528762757e433cd50de35bcb3c1 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 1eacd47636a9de5bee25d9d5962dc538a82d9f0b affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 8aa8a40c766b3945b40565a70349d5581458ff63 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< c036f5f2680cbdabdbbace86baee3c83721634d6 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 4c2d14c40a68678d885eab4008a0129646805bae affected
… +10 more rows
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I. Basic Information for CVE-2025-21922

Vulnerability Information
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Vulnerability Title
ppp: Fix KMSAN uninit-value warning with bpf
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ppp: Fix KMSAN uninit-value warning with bpf Syzbot caught an "KMSAN: uninit-value" warning [1], which is caused by the ppp driver not initializing a 2-byte header when using socket filter. The following code can generate a PPP filter BPF program: ''' struct bpf_program fp; pcap_t *handle; handle = pcap_open_dead(DLT_PPP_PPPD, 65535); pcap_compile(handle, &fp, "ip and outbound", 0, 0); bpf_dump(&fp, 1); ''' Its output is: ''' (000) ldh [2] (001) jeq #0x21 jt 2 jf 5 (002) ldb [0] (003) jeq #0x1 jt 4 jf 5 (004) ret #65535 (005) ret #0 ''' Wen can find similar code at the following link: https://github.com/ppp-project/ppp/blob/master/pppd/options.c#L1680 The maintainer of this code repository is also the original maintainer of the ppp driver. As you can see the BPF program skips 2 bytes of data and then reads the 'Protocol' field to determine if it's an IP packet. Then it read the first byte of the first 2 bytes to determine the direction. The issue is that only the first byte indicating direction is initialized in current ppp driver code while the second byte is not initialized. For normal BPF programs generated by libpcap, uninitialized data won't be used, so it's not a problem. However, for carefully crafted BPF programs, such as those generated by syzkaller [2], which start reading from offset 0, the uninitialized data will be used and caught by KMSAN. [1] https://syzkaller.appspot.com/bug?extid=853242d9c9917165d791 [2] https://syzkaller.appspot.com/text?tag=ReproC&x=11994913980000
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于未初始化PPP BPF程序头。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 ~ d685096c8129c9a92689975193e268945fd21dbf -
Linux Linux 2.6.12 -

II. Public POCs for CVE-2025-21922

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III. Intelligence Information for CVE-2025-21922

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Same Patch Batch · Linux · 2025-04-01 · 93 CVEs total

CVE-2025-21927 9.8 CRITICAL nvme-tcp: fix potential memory corruption in nvme_tcp_recv_pdu()
CVE-2025-21954 9.8 CRITICAL netmem: prevent TX of unreadable skbs
CVE-2025-21969 8.8 HIGH Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd
CVE-2025-21955 8.8 HIGH ksmbd: prevent connection release during oplock break notification
CVE-2025-21972 8.8 HIGH net: mctp: unshare packets when reassembling
CVE-2025-21946 8.8 HIGH ksmbd: fix out-of-bounds in parse_sec_desc()
CVE-2025-21945 8.8 HIGH ksmbd: fix use-after-free in smb2_lock
CVE-2025-21967 8.8 HIGH ksmbd: fix use-after-free in ksmbd_free_work_struct
CVE-2025-21947 8.1 HIGH ksmbd: fix type confusion via race condition when using ipc_msg_send_request
CVE-2025-21934 7.8 HIGH rapidio: fix an API misues when rio_add_net() fails
CVE-2025-21923 7.8 HIGH HID: hid-steam: Fix use-after-free when detaching device
CVE-2025-21949 7.8 HIGH LoongArch: Set hugetlb mmap base address aligned with pmd size
CVE-2025-21919 7.8 HIGH sched/fair: Fix potential memory corruption in child_cfs_rq_on_list
CVE-2025-21914 7.8 HIGH slimbus: messaging: Free transaction ID in delayed interrupt scenario
CVE-2025-21924 7.8 HIGH net: hns3: make sure ptp clock is unregister and freed if hclge_ptp_get_cycle returns an e
CVE-2025-21958 7.8 HIGH Revert "openvswitch: switch to per-action label counting in conntrack"
CVE-2025-21965 7.8 HIGH sched_ext: Validate prev_cpu in scx_bpf_select_cpu_dfl()
CVE-2025-21926 7.8 HIGH net: gso: fix ownership in __udp_gso_segment
CVE-2025-21939 7.8 HIGH drm/xe/hmm: Don't dereference struct page pointers without notifier lock
CVE-2025-21985 7.8 HIGH drm/amd/display: Fix out-of-bound accesses

Showing top 20 of 93 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-21922

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