xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata()
In the Linux kernel, the following vulnerability has been resolved: xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata() The TX metadata area resides in the UMEM buffer which is memory-mapped and concurrently writable by userspace. In xsk_skb_metadata(), csum_start and csum_offset are read from shared memory for bounds validation, then read again for skb assignment. A malicious userspace application can race to overwrite these values between the two reads, bypassing the bounds check and causing out-of-bounds memory access during checksum computation in the transmit path. Fix this by reading csum_start and csum_offset into local variables once, then using the local copies for both validation and assignment. Note that other metadata fields (flags, launch_time) and the cached csum fields may be mutually inconsistent due to concurrent userspace writes, but this is benign: the only security-critical invariant is that each field's validated value is the same one used, which local caching guarantees.
CVE-2026-53250
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-53250
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "48eb03dd26304c24f03bdbb9382e89c8564e71df",
"lessThan": "eb778aed8a9b2381668fcb1247ae4fa011224768",
"versionType": "git"
},
{
"status": "affected",
"version": "48eb03dd26304c24f03bdbb9382e89c8564e71df",
"lessThan": "0dfe05b938435892875e07771170051346412df9",
"versionType": "git"
},
{
"status": "affected",
"version": "48eb03dd26304c24f03bdbb9382e89c8564e71df",
"lessThan": "bfdfd2706d5fb2cd496a1506e680daf979309c8b",
"versionType": "git"
},
{
"status": "affected",
"version": "48eb03dd26304c24f03bdbb9382e89c8564e71df",
"lessThan": "22ba97ea9cc1f63a0d0244fae38057ed452b6ac7",
"versionType": "git"
}
],
"programFiles": [
"net/xdp/xsk.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.8"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.8",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.110",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.36",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.0.13",
"versionType": "semver",
"lessThanOrEqual": "7.0.*"
},
{
"status": "unaffected",
"version": "7.1",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/xdp/xsk.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-53250
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #40793 · Revision 1
- Added to Heist Feed
- Publisher date