CVE-2026-74478
um: vector: fix use-after-free in vector_mmsg_rx()
Description
In the Linux kernel, the following vulnerability has been resolved: um: vector: fix use-after-free in vector_mmsg_rx() When vector_mmsg_rx() discards a packet whose overlay header fails verify_header(), it frees the skb and continues the loop: if (header_check < 0) { dev_kfree_skb_irq(skb); vp->estats.rx_encaps_errors++; continue; } The normal and short-packet paths fall through to the bottom of the loop body, which clears the consumed slot and advances the cursors: (*skbuff_vector) = NULL; mmsg_vector++; skbuff_vector++; The verify_header() < 0 path skips that via continue, so the freed skb is left in skbuff_vector[] and the cursors do not advance. The next iteration reads the same slot, gets the freed skb, and frees it again, producing a refcount underflow / use-after-free in the RX path. Discard the slot the same way the other paths do before continuing. Only transports whose verify_header() can return negative are affected: GRE and L2TPv3 do so on a cookie/session-id mismatch (raw/tap do not), so any peer on such a transport can trigger it without authentication.
INFO
Published Date :
Aug. 15, 2026, 1:17 p.m.
Last Modified :
Aug. 15, 2026, 1:17 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Affected Products
The following products are affected by CVE-2026-74478
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
Solution
- Apply the kernel patch for the vector_mmsg_rx() vulnerability.
- Discard the slot before continuing the loop.
- Ensure skb is freed and cursors advance correctly.
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-2026-74478.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-74478 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-2026-74478
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-2026-74478 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-74478 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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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Aug. 15, 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': '49da7e64f33e80edffb1a9eeb230fa4c3f42dffb', 'lessThan': '4b9601595e8b6b5d18878cac0aeabc687d241111', 'versionType': 'git'}, {'status': 'affected', 'version': '49da7e64f33e80edffb1a9eeb230fa4c3f42dffb', 'lessThan': '67d58ab4f2ccf7145f3da07e025735a09c79de1b', 'versionType': 'git'}, {'status': 'affected', 'version': '49da7e64f33e80edffb1a9eeb230fa4c3f42dffb', 'lessThan': '180ff4c81faf01ec4e06082c9daa7c40518ead89', 'versionType': 'git'}, {'status': 'affected', 'version': '49da7e64f33e80edffb1a9eeb230fa4c3f42dffb', 'lessThan': '804b681002ead233abf49a3efd681f5468a835f9', 'versionType': 'git'}, {'status': 'affected', 'version': '49da7e64f33e80edffb1a9eeb230fa4c3f42dffb', 'lessThan': 'af421e9aed3920c7ac88c24daa48606c7112feca', 'versionType': 'git'}], 'programFiles': ['arch/um/drivers/vector_kern.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '4.17'}, {'status': 'unaffected', 'version': '0', 'lessThan': '4.17', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '6.6.151', 'versionType': 'semver', 'lessThanOrEqual': '6.6.*'}, {'status': 'unaffected', 'version': '6.12.103', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.44', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.1.8', 'versionType': 'semver', 'lessThanOrEqual': '7.1.*'}, {'status': 'unaffected', 'version': '7.2-rc6', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['arch/um/drivers/vector_kern.c'], 'defaultStatus': 'affected'}] Added Description In the Linux kernel, the following vulnerability has been resolved: um: vector: fix use-after-free in vector_mmsg_rx() When vector_mmsg_rx() discards a packet whose overlay header fails verify_header(), it frees the skb and continues the loop: if (header_check < 0) { dev_kfree_skb_irq(skb); vp->estats.rx_encaps_errors++; continue; } The normal and short-packet paths fall through to the bottom of the loop body, which clears the consumed slot and advances the cursors: (*skbuff_vector) = NULL; mmsg_vector++; skbuff_vector++; The verify_header() < 0 path skips that via continue, so the freed skb is left in skbuff_vector[] and the cursors do not advance. The next iteration reads the same slot, gets the freed skb, and frees it again, producing a refcount underflow / use-after-free in the RX path. Discard the slot the same way the other paths do before continuing. Only transports whose verify_header() can return negative are affected: GRE and L2TPv3 do so on a cookie/session-id mismatch (raw/tap do not), so any peer on such a transport can trigger it without authentication. Added Reference https://git.kernel.org/stable/c/180ff4c81faf01ec4e06082c9daa7c40518ead89 Added Reference https://git.kernel.org/stable/c/4b9601595e8b6b5d18878cac0aeabc687d241111 Added Reference https://git.kernel.org/stable/c/67d58ab4f2ccf7145f3da07e025735a09c79de1b Added Reference https://git.kernel.org/stable/c/804b681002ead233abf49a3efd681f5468a835f9 Added Reference https://git.kernel.org/stable/c/af421e9aed3920c7ac88c24daa48606c7112feca