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CVE-2025-21922

Vulnérabilité moyenne dans Linux (Linux)

CVSS 5.5 · Moyenne
EPSS 0.2%
Linux•Linux•Versions : <=6.1.*, 6.6.83, <2f591cb158807bdcf424f66f1fbfa6e4e50f3757, <=6.12.*, 6.1.131, 2.6.12, 0, <3de809a768464528762757e433cd50de35bcb3c1, <2.6.12, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, <d685096c8129c9a92689975193e268945fd21dbf, 6.12.19, 6.14, 6.13.7, <=5.10.*, <=6.6.*, <8aa8a40c766b3945b40565a70349d5581458ff63, <1eacd47636a9de5bee25d9d5962dc538a82d9f0b, <=5.4.*, 5.4.291, <4e2191b0fd0c064d37b0db67396216f2d4787e0f, <4c2d14c40a68678d885eab4008a0129646805bae, 5.15.179, <c036f5f2680cbdabdbbace86baee3c83721634d6, <=*, <=5.15.*, 5.10.235, <=6.13.*

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

Gravité et risque d'exploitation

CVE-2025-21922 obtient un score CVSS de 5.5/10, soit une gravité moyenne. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.23 %, ce qui la place devant 12.8 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions <=6.1.*, 6.6.83, <2f591cb158807bdcf424f66f1fbfa6e4e50f3757, <=6.12.*, 6.1.131, 2.6.12, 0, <3de809a768464528762757e433cd50de35bcb3c1, <2.6.12, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, <d685096c8129c9a92689975193e268945fd21dbf, 6.12.19, 6.14, 6.13.7, <=5.10.*, <=6.6.*, <8aa8a40c766b3945b40565a70349d5581458ff63, <1eacd47636a9de5bee25d9d5962dc538a82d9f0b, <=5.4.*, 5.4.291, <4e2191b0fd0c064d37b0db67396216f2d4787e0f, <4c2d14c40a68678d885eab4008a0129646805bae, 5.15.179, <c036f5f2680cbdabdbbace86baee3c83721634d6, <=*, <=5.15.*, 5.10.235, <=6.13.*) est présent sur votre parc.
  • Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
  • À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
  • Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

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