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Review reviewCritical

CVE-2026-63993

Linux

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.

CVSS
9.8
EPSS
-
- percentile
CISA KEV
Not listed
Published
2026.07.20
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 9.8

Vulnerability overview

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.

Affected product and versions

Product
Linux
Affected versions
>= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f < 6b8bfce9d2f774d2c2243e0248e03efb99bba6c0, >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f < 9257f56ac47ef1976bcd056cf986a9988eeec67a, >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f < 8d435d68d71fb875876b722f4136caf74f2f48bd, >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f < dc3bfa050f873371e745bdf478b1f5b738e5733d, >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f < 609e63312c29aad18026a1d3222e123d4b6b0feb, >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f < 5303925e360527243b46a440a04667826bbc72b7, >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f < a493efd4336cf19122ae0e4cbb3d31b32d70deea, >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f < 7d9ef0cb271555d8cf39fefe6c981e1493b25ecf, >= 5.9
Fixed versions
No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE
Not available