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CVE-2025-21891

5.5 · MEDIUM

In the Linux kernel, the following vulnerability has been resolved: ipvlan: ensure network headers are in skb linear part syzbot found that ipvlan_process_v6_outbound() was assuming the IPv6 netw…

Published Mar 27, 2025CWE-908EPSS 0.19%

Overview

CVE-2025-21891 is a medium-severity vulnerability. It was published on March 27, 2025 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

In the Linux kernel, the following vulnerability has been resolved:

ipvlan: ensure network headers are in skb linear part

syzbot found that ipvlan_process_v6_outbound() was assuming

the IPv6 network header isis present in skb->head [1]

Add the needed pskb_network_may_pull() calls for both

IPv4 and IPv6 handlers.

[1]

BUG: KMSAN: uninit-value in __ipv6_addr_type+0xa2/0x490 net/ipv6/addrconf_core.c:47

__ipv6_addr_type+0xa2/0x490 net/ipv6/addrconf_core.c:47

ipv6_addr_type include/net/ipv6.h:555 [inline]

ip6_route_output_flags_noref net/ipv6/route.c:2616 [inline]

ip6_route_output_flags+0x51/0x720 net/ipv6/route.c:2651

ip6_route_output include/net/ip6_route.h:93 [inline]

ipvlan_route_v6_outbound+0x24e/0x520 drivers/net/ipvlan/ipvlan_core.c:476

ipvlan_process_v6_outbound drivers/net/ipvlan/ipvlan_core.c:491 [inline]

ipvlan_process_outbound drivers/net/ipvlan/ipvlan_core.c:541 [inline]

ipvlan_xmit_mode_l3 drivers/net/ipvlan/ipvlan_core.c:605 [inline]

ipvlan_queue_xmit+0

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/27843ce6ba3d3122b65066550fe33fb8839f8aefRefgit.kernel.org/stable/c/4ec48f812804f370f622e0874e6dd8fcc58241cdRefgit.kernel.org/stable/c/5353fd89663c48f56bdff975c562cfe78b1a2e4cRefgit.kernel.org/stable/c/5b8dea8d1612dc7151d2457d7d2e6a69820309bfRefgit.kernel.org/stable/c/e2a4f76a2d8a44816ecd25bcbdb47b786d621974Reflists.debian.org/debian-lts-announce/2025/05/msg00045.html

How CyberStrike helps

Frequently asked questions

What is CVE-2025-21891?

CVE-2025-21891 is a medium-severity vulnerability. It was published on March 27, 2025 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-21891?

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2025-21891?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2025-21891?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2025-21891 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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