CVE-2026-63993
vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()
Description
In the Linux kernel, the following vulnerability has been resolved: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu() skb_tunnel_check_pmtu() can change skb->head. Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF. Use instead ip_hdr(skb) as done in drivers/net/bareudp.c and drivers/net/geneve.c. Found by Sashiko.
INFO
Published Date :
July 19, 2026, 4:17 p.m.
Last Modified :
July 30, 2026, 2:51 p.m.
Remotely Exploit :
Yes !
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | CRITICAL | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 |
Solution
- Update the Linux kernel.
- Ensure IP header is accessed after PMTU check.
- Use ip_hdr(skb) for IP header access.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-63993.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-63993 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-63993
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-63993 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-63993 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Jul. 20, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H -
New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Jul. 19, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': '6b8bfce9d2f774d2c2243e0248e03efb99bba6c0', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': '9257f56ac47ef1976bcd056cf986a9988eeec67a', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': '8d435d68d71fb875876b722f4136caf74f2f48bd', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': 'dc3bfa050f873371e745bdf478b1f5b738e5733d', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': '609e63312c29aad18026a1d3222e123d4b6b0feb', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': '5303925e360527243b46a440a04667826bbc72b7', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': 'a493efd4336cf19122ae0e4cbb3d31b32d70deea', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': '7d9ef0cb271555d8cf39fefe6c981e1493b25ecf', 'versionType': 'git'}], 'programFiles': ['drivers/net/vxlan/vxlan_core.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '5.9'}, {'status': 'unaffected', 'version': '0', 'lessThan': '5.9', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '5.10.259', 'versionType': 'semver', 'lessThanOrEqual': '5.10.*'}, {'status': 'unaffected', 'version': '5.15.210', 'versionType': 'semver', 'lessThanOrEqual': '5.15.*'}, {'status': 'unaffected', 'version': '6.1.176', 'versionType': 'semver', 'lessThanOrEqual': '6.1.*'}, {'status': 'unaffected', 'version': '6.6.143', 'versionType': 'semver', 'lessThanOrEqual': '6.6.*'}, {'status': 'unaffected', 'version': '6.12.93', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.35', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.0.12', 'versionType': 'semver', 'lessThanOrEqual': '7.0.*'}, {'status': 'unaffected', 'version': '7.1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['drivers/net/vxlan/vxlan_core.c'], 'defaultStatus': 'affected'}] Added Description In the Linux kernel, the following vulnerability has been resolved: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu() skb_tunnel_check_pmtu() can change skb->head. Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF. Use instead ip_hdr(skb) as done in drivers/net/bareudp.c and drivers/net/geneve.c. Found by Sashiko. Added Reference https://git.kernel.org/stable/c/5303925e360527243b46a440a04667826bbc72b7 Added Reference https://git.kernel.org/stable/c/609e63312c29aad18026a1d3222e123d4b6b0feb Added Reference https://git.kernel.org/stable/c/6b8bfce9d2f774d2c2243e0248e03efb99bba6c0 Added Reference https://git.kernel.org/stable/c/7d9ef0cb271555d8cf39fefe6c981e1493b25ecf Added Reference https://git.kernel.org/stable/c/8d435d68d71fb875876b722f4136caf74f2f48bd Added Reference https://git.kernel.org/stable/c/9257f56ac47ef1976bcd056cf986a9988eeec67a Added Reference https://git.kernel.org/stable/c/a493efd4336cf19122ae0e4cbb3d31b32d70deea Added Reference https://git.kernel.org/stable/c/dc3bfa050f873371e745bdf478b1f5b738e5733d