CVE-2026-63992
tunnels: do not assume transport header in iptunnel_pmtud_check_icmp()
Description
In the Linux kernel, the following vulnerability has been resolved: tunnels: do not assume transport header in iptunnel_pmtud_check_icmp() In some cases, iptunnel_pmtud_check_icmp() can be called while skb transport header is not set. This triggers an out-of-bound access, because (typeof(skb->transport_header))~0U is 65535. Access the icmp header based on IPv4 network header, after making sure icmp->type is present in skb linear part. Note that iptunnel_pmtud_check_icmpv6()) is fine.
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
- Apply the Linux kernel patch for tunnel vulnerability.
- Validate skb transport header before access.
- Ensure ICMP header is present in the linear part.
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-2026-63992.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-63992 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-2026-63992
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).
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The following list is the news that have been mention
CVE-2026-63992 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-63992 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.
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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:N/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': '5a92cb45e34749865d03daf8d3500f77b5f6644c', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': 'c7b7ec3e69e673c0d6b57f74d21da50c485c598e', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': '7f4f7efe7f30edd29c4988de01728bf2398217e4', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': 'e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': 'a096b6e34f602950af9a2b0856cd93a5f4c276d7', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': '43368636c663cff6e59dde93cf4b8e43ac28eb93', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': 'cb549df9ce4ee15c9d5b19ddab12cf2128e4313c', 'versionType': 'git'}, {'status': 'affected', 'version': '4cb47a8644cc9eb8ec81190a50e79e6530d0297f', 'lessThan': '509323077ef79a26ba0c60bb556e45c12c398b2d', 'versionType': 'git'}], 'programFiles': ['net/ipv4/ip_tunnel_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': ['net/ipv4/ip_tunnel_core.c'], 'defaultStatus': 'affected'}] Added Description In the Linux kernel, the following vulnerability has been resolved: tunnels: do not assume transport header in iptunnel_pmtud_check_icmp() In some cases, iptunnel_pmtud_check_icmp() can be called while skb transport header is not set. This triggers an out-of-bound access, because (typeof(skb->transport_header))~0U is 65535. Access the icmp header based on IPv4 network header, after making sure icmp->type is present in skb linear part. Note that iptunnel_pmtud_check_icmpv6()) is fine. Added Reference https://git.kernel.org/stable/c/43368636c663cff6e59dde93cf4b8e43ac28eb93 Added Reference https://git.kernel.org/stable/c/509323077ef79a26ba0c60bb556e45c12c398b2d Added Reference https://git.kernel.org/stable/c/5a92cb45e34749865d03daf8d3500f77b5f6644c Added Reference https://git.kernel.org/stable/c/7f4f7efe7f30edd29c4988de01728bf2398217e4 Added Reference https://git.kernel.org/stable/c/a096b6e34f602950af9a2b0856cd93a5f4c276d7 Added Reference https://git.kernel.org/stable/c/c7b7ec3e69e673c0d6b57f74d21da50c485c598e Added Reference https://git.kernel.org/stable/c/cb549df9ce4ee15c9d5b19ddab12cf2128e4313c Added Reference https://git.kernel.org/stable/c/e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec