bpf: Reject tail calls directly from callback frames
In the Linux kernel, the following vulnerability has been resolved: bpf: Reject tail calls directly from callback frames A tail call from a non-zero frame is modeled as a return from that frame. The verifier makes R0 unknown and calls prepare_func_exit() for the taken branch. When the current frame is a synchronous callback, prepare_func_exit() enforces the callback return-value contract and marks R0 precise. Since the tail-call path synthesized R0 rather than deriving it from an instruction, precision backtracking reaches the callback-calling instruction with R0 still requested and triggers the "callback unexpected regs" verifier bug. A CAP_BPF task can therefore cause a WARN and an -EFAULT BPF_PROG_LOAD. Tail calls reachable from callbacks are already rejected later by check_max_stack_depth(). Reject a tail call made directly by a callback before constructing the inconsistent return state, using the existing diagnostic. Tail calls from ordinary subprograms keep their current behavior.
CVE-2026-98061
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-2026-98061
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": "a6c22c91b6284e4713c0cf5b20ab3c9c71b77ae8",
"lessThan": "617c8266e49f45747f71e74177646a63f72b7025",
"versionType": "git"
},
{
"status": "affected",
"version": "e3245f8990431950d20631c72236d4e8cb2dcde8",
"lessThan": "96d31b28263c429a56e4de85bcf744a5c320b3a3",
"versionType": "git"
},
{
"status": "affected",
"version": "e3245f8990431950d20631c72236d4e8cb2dcde8",
"lessThan": "266aa4ad0b2e82397cd9045752c9bff03d98eddd",
"versionType": "git"
},
{
"status": "affected",
"version": "6.18.2",
"lessThan": "6.18.53",
"versionType": "semver"
}
],
"programFiles": [
"kernel/bpf/verifier.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.19"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.19",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.18.53",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.7",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"kernel/bpf/verifier.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-98061
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #38173 · Revision 1
- Added to Heist Feed
- Publisher date